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解决 Windows PowerShell 测试 SMTP 端口失败的问题:以 219.156.123.221 为例

在日常网络排障或邮件服务器配置过程中,我们常会使用 Test-NetConnection 命令来测试远程主机某个端口是否开放。近期,在一台 Windows Server 上执行如下命令时,遇到了无法连接到目标服务器 25 端口的问题:

Test-NetConnection -ComputerName 219.156.123.221 -Port 25

测试结果如下所示:

ComputerName           : 219.156.123.221
RemoteAddress          : 219.156.123.221
RemotePort             : 25
InterfaceAlias         : WLAN 2
SourceAddress          : 10.168.1.158
PingSucceeded          : True
PingReplyDetails (RTT) : 3 ms
TcpTestSucceeded       : False

从输出可以看出,虽然目标主机 219.156.123.221 可以 ping 通(PingSucceeded: True),但 TCP 测试连接失败(TcpTestSucceeded: False),也就是说 25 端口无法建立连接

接下来我们将从多个角度分析可能的原因,并提供相应的解决方案。


一、常见原因分析及解决思路

1. 目标服务器未监听 25 端口

邮件服务是否真正运行在目标主机上是首要判断的点。很多情况下,服务端口未正确启用或监听地址配置错误都会导致连接失败。

解决方案:
在目标服务器上检查是否有 SMTP 服务(如 Postfix、Sendmail、Exchange)运行,并绑定了 25 端口:

  • Linux:

    netstat -tlnp | grep :25
    

    ss -tlnp | grep :25
    
  • Windows:

    netstat -ano | findstr :25
    

确认服务已监听 0.0.0.0:25 或目标 IP 地址的 25 端口。


2. 目标服务器防火墙阻止了 25 端口

即便服务监听成功,若防火墙未开放相应端口,同样会导致外部连接失败。

解决方案:

  • 检查 Windows 防火墙或 Linux 防火墙配置(如 firewalldiptables);

  • 确保入站规则中允许 TCP 端口 25;

  • 在云服务器上,还需检查安全组规则是否开放该端口。


3. 中间网络设备或 ISP 封锁了端口 25

许多运营商(ISP)为防止滥发垃圾邮件,默认封锁 25 端口的出入站访问。这种限制在家庭宽带和一些云主机中十分常见。

解决方案:

  • 联系服务提供商确认是否封锁了端口 25;

  • 尝试使用 587(SMTP over TLS)465(SMTP over SSL) 端口替代发送邮件;

  • 更换网络环境或通过 VPN 测试是否为本地网络问题。

建议测试:

Test-NetConnection -ComputerName 219.156.123.221 -Port 587
Test-NetConnection -ComputerName 219.156.123.221 -Port 465

4. 本地网络或系统出站策略限制

如果你在局域网、办公网络或使用了代理,路由器或防火墙可能拦截了 TCP 出站连接到 25 端口。

解决方案:

  • 检查路由器或企业防火墙策略;

  • 查看 Windows 本地防火墙出站规则是否存在限制;

  • 若有代理或网关,也需确保其允许连接外部 SMTP 服务。


二、其他配置建议

若你正在配置邮件服务器(例如在 Windows Server 上部署 Exchange 或在 Linux 上部署 Postfix),确保如下配置正确:

  • 邮件服务已启动并监听 25、587 或 465 端口;

  • 公网 IP 地址及 MX、PTR 记录设置正确;

  • 域名已配置 SPF、DKIM、DMARC 等防伪记录;

  • 所有相关端口已在本地防火墙与云安全组中放行;

  • 测试连接时使用的是服务器实际监听的 IP 与端口。


三、总结

Test-NetConnection 是 Windows PowerShell 下测试网络连通性与端口开放性的实用工具。当 TcpTestSucceededFalse 时,我们需从 服务监听状态、防火墙配置、运营商限制、出站策略 等角度逐一排查。

邮件服务的正常运行依赖网络层的稳定和开放性。尤其是在配置 SMTP 服务时,建议优先使用 587 端口进行邮件传输,以避开常见的端口封锁问题。

如仍无法解决问题,建议结合服务器系统日志、邮件服务日志以及 Wireshark 等抓包工具进一步分析通信细节。

The Weight of Tomorrow

Dr. Eric Jefferson stood at the edge of the grand auditorium in San Francisco, his palms slightly damp as he adjusted his tie. The Global Tech Summit buzzed with energy—economists, tech moguls, and policymakers from across the world filled the room, their voices a cacophony of optimism and caution. The topic dominating the agenda was artificial intelligence, a force that promised to reshape economies, societies, and lives. Eric, an economics professor from MIT, had been invited to share his perspective, but he felt the weight of skepticism pressing against his chest. The world was enamored with AI’s potential, but he saw a more complex truth—one that history had taught him to respect.

As he stepped onto the stage, the lights dimmed, and a hush fell over the crowd. Eric cleared his throat, his gaze sweeping over faces lit by the glow of laptops and tablets. “Good morning,” he began, his voice steady but deliberate. “Today, I want to talk about why our excitement for artificial intelligence—and other transformative technologies like Bitcoin—might be outpacing their real-world impact. Not because they lack potential, but because societies take time to adapt.”

He paused, letting the words settle. “Let’s start with AI. In the United States, we’re a nation of contrasts. We’re optimistic by nature—yet, if you look at the data, only 6% of Americans believe the future will be better. In China, that number is 41%. Why the difference? Americans are worried. They fear that AI, if widely adopted, could erode the middle class. Globalization already siphoned off jobs; now, AI threatens to widen the wealth gap further. People are asking: will machines take our livelihoods? Will inequality spiral out of control?”

Eric clicked to his first slide, a graph showing U.S. productivity trends. “Productivity is the backbone of prosperity, yet America’s productivity growth is stagnant. Since the 1970s, it’s hovered around 1.2% annually—dismal compared to post-World War II highs. Low productivity fuels inequality. Wages stagnate, the middle class grows restless, and social discontent festers. AI, we’re told, will change this. It’s a revolution waiting to happen. But is it?”

He leaned forward, his voice dropping. “Here’s the paradox: technological innovation hasn’t slowed. In the last decade, AI has birthed breakthroughs—machine learning, deep learning, neural networks, speech recognition, image recognition. Giants like Google, Apple, Amazon, and Microsoft are pouring billions into AI, believing it’s on the cusp of a ‘final breakthrough.’ Since 2012, AI investment has grown tenfold. The optimism is palpable. So why hasn’t this translated into a productivity boom?”

Eric paced the stage, his thoughts drifting to a conversation he’d had the previous night with a young engineer from Silicon Valley. The engineer had gushed about AI’s potential to “solve everything,” from healthcare to transportation. Eric had smiled politely but thought of history’s lessons—promises that never quite materialized. “Let me take you back,” he said to the audience. “In the 1960s, scientists believed nuclear energy would solve humanity’s energy crisis. It was the ultimate solution—cheap, abundant power. Yet, half a century later, nuclear energy still can’t compete economically with oil or gas. Controlled nuclear fusion? Always ‘twenty years away,’ even after sixty years. Space exploration? We landed on the moon in 1969 and thought Mars was next by the 1980s. Forty years later, we haven’t returned to the moon.”

He chuckled softly, shaking his head. “And don’t get me started on flying cars. In the 1950s, we imagined cars sprouting wings, soaring above cities. Yet those blueprints never left the ground. Biofuels in the 1990s? Hyped as the answer to oil dependency, but the companies behind them vanished. Even AI itself isn’t new—its concept emerged in 1967, with promises of surpassing human intelligence. We’re still waiting.”

Eric’s tone grew serious. “This is my first point: technologists often overestimate the immediate impact of their inventions. They believe technology can solve every societal ill, but history shows otherwise. When I was a child, magazines like *Scientific American* painted visions of cities filled with flying spaceships by the year 2000. Two hundred years later, we’re still grounded. Why? Because technical optimism is a bias. It’s fueled by technologists’ faith, amplified by capital markets hungry for the next big thing and media chasing clicks. Every year, we’re promised a ‘revolution.’ But revolutions are rarely recognized in their infancy—they’re only clear in hindsight, decades later. What’s sold as a revolution often ends as a bubble.”

He moved to his second point, projecting a new slide. “My second argument is about measurement. Our economic metrics may be understating technology’s impact. Productivity statistics are often outdated, lagging behind reality. This isn’t new—economists have long debated whether our tools capture the full value of innovation.”

Eric’s mind flashed to a dinner he’d attended with colleagues, where a heated debate had erupted over whether AI’s benefits were concentrated among a few industries. “Which brings me to my third point,” he continued. “Technological breakthroughs often benefit a select few—specific sectors, specific people. AI is no exception. It’s transformative, but its gains are unevenly distributed.”

He paused, then smiled. “But my fourth point is the one I find most compelling. Major technological breakthroughs—like AI—require society to reorganize itself. And that takes time. AI isn’t just a tool; it’s a general-purpose technology, like the steam engine, electricity, computers, or the internet. These technologies share three traits: they spread across industries, they improve continuously, and they spark chain innovations—new industries, new business models, new ways of living.”

Eric’s voice grew animated as he recounted history. “Take the steam engine. It started in coal mines, draining water. Then it powered trains and ships, revolutionizing transport. Electricity? Discovered in the early 19th century, it wasn’t until the 1890s that electric motors entered U.S. industry. By 1919—thirty years later—over half of American factories used electricity. But in those early decades, productivity barely budged, growing just 1.2% annually. Why? Because factories were still designed for steam. Power was centralized, with one massive steam engine driving gears and belts. When electric motors arrived, they were initially just a cheaper substitute—no fundamental change.”

He leaned into the podium. “Then came standalone motors. Suddenly, factories could place smaller motors on each machine, freeing up layouts. This led to the assembly line—Ford’s great revolution. Production costs plummeted, efficiency soared. People moved to suburbs, drove cars, and American life transformed. But it took thirty years for electricity to reshape society.”

Eric shifted to a more recent example. “Now, let’s look at the IT revolution. It began in 1971 with Intel’s first commercial CPU, the 4004. A marvel, but primitive compared to today’s smartphones. Yet, from 1971 to the mid-1990s, U.S. productivity growth was abysmal—1.3% in the 1970s, 1.7% in the 1980s. It wasn’t until 1995, with Netscape Navigator and graphical browsers, that the internet sparked a true transformation. E-commerce, mobile apps, new business models—all emerged after a 25-year gestation. Only then did productivity surge.”

He paused, letting the audience absorb the pattern. “Whether it’s electricity or IT, it takes 25 to 30 years for society to adapt. Companies must reorganize, workers must retrain, and entire systems must shift. I saw this myself in 1994, as a graduate student discovering email. It was primitive—no graphical browsers, just text commands. I emailed a high school friend in Ohio, marveling at the speed. But why use email over a phone or fax? Cost. Long-distance calls were expensive. Email was a tool for efficiency, not transformation—until the internet matured.”

Eric’s thoughts turned to the present. “AI is no different. It’s spreading across industries—finance, healthcare, beyond IT. Its algorithms improve daily, and it’s sparking chain innovations. But society needs time to adapt. Look at factories in places like Dongguan, China, where automation is replacing workers. Only 10% of frontline workers can learn to program robots. The rest? They return to villages or take jobs as delivery drivers. Older workers resist change—they’re comfortable with old methods. Younger generations, born with technology, lead the way.”

He gestured to the audience. “Think about your social circles. In tech, most innovators are in their 20s and 30s. Older employees struggle to keep up, burdened by responsibilities. The future of AI will likely be driven by those born after 2000—digital natives with AI in their DNA. Companies like Google or Microsoft know this. They’re investing heavily, but even they face challenges. Google acquired nine robotics firms, hoping to dominate AI. Yet integration has faltered—talent leaves, startups emerge. The lesson? No matter how rich a company is, it can’t monopolize innovation. Young, knowledge-driven firms will always challenge the old guard.”

Eric’s lecture shifted to another disruptive force: Bitcoin. “Let’s pivot to another technology reshaping our world,” he said, clicking to a slide of a digital coin. “Bitcoin is a fascinating case. Its market is small—hundreds of billions—but it’s a battleground. Right now, it’s a guerrilla war, with pricing power in the hands of Bitcoin’s ‘miners’ and early adopters. But as its market grows to trillions, Wall Street will step in, turning it into a plains war—a structured battlefield of futures, ETFs, and derivatives.”

He recounted Wall Street’s strategy: legitimize Bitcoin through regulated exchanges like Chicago’s, then introduce ETFs to draw retail investors. “Once the market scales, derivatives will dwarf physical Bitcoin trading. Pricing power will shift to those who don’t even own Bitcoin—speculators betting against it. Just like gold, once the king of money, Bitcoin risks being tamed by Wall Street. They can’t destroy it, so they’ll co-opt it, inviting it from the mountains to the plains where they hold the advantage.”

Eric’s mind wandered to a late-night conversation with a colleague about Bitcoin’s value. “Is Bitcoin a currency, an asset, or a digital service?” he asked the audience. “It has currency traits: a medium of exchange, accepted by some e-commerce platforms and even Japanese firms for salaries; a unit of account, with countries like Germany considering its use for debts and taxes; and a store of value, thanks to its 21-million-coin cap. But a good currency must be stable. Bitcoin’s volatility—surging 18-fold or crashing 50%—makes it unreliable for trade. Stores hesitate to accept it, fearing losses.”

He continued, “As an asset, Bitcoin lacks cash flow, like a Van Gogh painting or gold jewelry. But those have intrinsic value—labor, creativity, mining costs. Bitcoin’s value lies in its blockchain, a ledger secured by immense computational power and electricity. Critics call this wasteful, but value always has a cost. Gold requires mining; fiat currency demands governmental discipline. Bitcoin’s cost is its security—a digital arms race that deters hackers.”

Eric’s voice softened. “But Bitcoin’s future isn’t guaranteed. Quantum computing could crack its encryption. MIT researchers estimate that while quantum computers won’t easily break Bitcoin’s ledger, they could reverse-engineer private keys, undermining trust. Nations are racing to build quantum machines, driven by military and intelligence goals. Bitcoin must upgrade its encryption within a shrinking window—perhaps five years, not ten.”

He concluded with a warning. “Bitcoin also faces competitors. Its blockchain is open-source, inspiring rivals. Imagine a digital currency backed by physical gold, stored in a vault with IoT chips for transparency. Such innovations could outshine Bitcoin, blending digital convenience with tangible value. Will Bitcoin remain a pioneer or become a martyr? Only time will tell.”

As Eric stepped off the stage, applause rippled through the room. He felt a mix of relief and unease. AI and Bitcoin were reshaping the world, but their promise came with a catch: society’s ability to adapt. History had shown that transformation was slow, uneven, and often painful. As he left the auditorium, he wondered if the next generation—those born with AI and blockchain in their veins—would navigate the future with more courage than caution.

AI Attitudes and Impact: A Comparative Analysis Contrasting Attitudes Toward AI

The perception of artificial intelligence (AI) varies significantly between the United States and China, reflecting broader cultural attitudes toward technological change. In the U.S., only about 6% of people believe the future will improve, according to statistical data, signaling a pervasive pessimism. In contrast, 41% of Chinese citizens express optimism about the future, embracing new technologies with enthusiasm. This stark contrast highlights a fundamental difference: Americans tend to view AI with apprehension, while the Chinese see it as an opportunity.

The primary concern in the U.S. centers on the potential for AI to exacerbate unemployment, particularly among the middle class. Globalization has already led to significant job losses, and the integration of AI raises fears of further employment displacement and widening wealth disparities. These concerns were a focal point at a recent forum, where an MIT economics professor, Erik Brynjolfsson, offered a compelling perspective on AI’s long-term and short-term impacts. His insights, which I’ll explore in detail, provide a nuanced understanding of AI’s role in society.

Professor Brynjolfsson’s Perspective

Professor Erik Brynjolfsson argues that while AI holds immense potential for transformative impact in the long run, its short-term effects on productivity are limited. This is particularly significant given the current state of U.S. productivity, which remains stagnant and contributes to growing social inequality. Low productivity growth has fueled wage stagnation and heightened dissatisfaction among the middle class, making it a critical root of societal discontent.

Surprisingly, Brynjolfsson notes that technological innovation, particularly in AI, has not slowed down. Fields like machine learning, deep learning, neural networks, speech recognition, and image recognition have seen remarkable advancements. Tech giants such as Google, Apple, Amazon, and Microsoft are heavily investing in AI, with investments increasing tenfold since 2012. These companies believe AI is on the cusp of a major breakthrough, poised to "take off" and reshape industries.

Yet, despite these advancements, AI has not yet driven a productivity revolution. Brynjolfsson identifies four reasons for this disconnect:

1. Overoptimism of Technologists

Technologists often overestimate the societal impact of emerging technologies. History offers numerous examples of such optimism. In the 1960s, scientists heralded nuclear energy as the ultimate solution to humanity’s energy needs, yet it remains economically unviable compared to fossil fuels. Similarly, controlled nuclear fusion has been perpetually "20 years away" for six decades. Space exploration, once expected to lead to Mars landings by the 1980s, has not progressed as anticipated. Concepts like flying cars or biofuels, hyped as revolutionary, have also failed to materialize as promised.

This pattern extends to AI. Proposed in 1967 as a technology that would surpass human intelligence, AI has yet to fully realize such lofty predictions. Technologists’ belief that technology can solve all societal problems often leads to exaggerated expectations. Additionally, capital markets and media amplify these claims to attract investment and generate buzz, creating a cycle of hype that rarely delivers immediate results. True technological revolutions often take decades to mature, only recognized as such in hindsight.

2. Flawed Productivity Metrics

Brynjolfsson suggests that current economic metrics may underestimate AI’s impact on productivity. Traditional indicators often lag behind technological advancements, failing to capture their full effect. This is not a new issue, as economists have long debated the accuracy of productivity measurements in reflecting technological progress.

3. Uneven Distribution of Benefits

AI’s benefits are currently concentrated in specific industries and among a small group of beneficiaries. This uneven distribution limits its broader societal impact, a phenomenon observed in previous technological shifts.

4. The Need for Societal Reorganization

The most insightful of Brynjolfsson’s points is that transformative technologies, like AI, require significant societal reorganization to realize their full potential. AI is a General Purpose Technology (GPT), akin to the steam engine, electricity, computers, and the internet. GPTs share three characteristics: pervasive diffusion across industries, continuous improvement, and the ability to spawn complementary innovations.

  • Diffusion: Like electricity, AI is spreading beyond IT to sectors like finance, healthcare, and more, with applications growing rapidly.
  • Improvement: AI algorithms are becoming more precise, and their scope is expanding, much like the performance doubling described by Moore’s Law in computing.
  • Complementary Innovations: AI fosters new industries, workflows, and business models, similar to how the internet revolutionized commerce and communication.

However, integrating a GPT into society takes time. Historical examples illustrate this. The electrification of U.S. industry, beginning in the 1890s, took nearly 30 years to significantly impact productivity. Initially, electric motors simply replaced steam engines without altering factory layouts or production models, resulting in minimal productivity gains (1.2% annually from 1890 to 1920). It was only with the invention of independent motors, enabling flexible factory designs and assembly lines, that productivity soared in the 1920s, transforming industries and lifestyles.

Similarly, the IT revolution, sparked by Intel’s 1971 commercial CPU, took 25 years to significantly boost productivity. Until the mid-1990s, IT applications focused on cost reduction and efficiency without fundamentally changing organizational structures. The introduction of graphical browsers like Netscape Navigator in 1995 marked a turning point, enabling e-commerce and new business models that reshaped society.

AI, as a GPT, will likely follow a similar trajectory, requiring 25–30 years for society to adapt through new organizational structures, workforce training, and business models. This adaptation is hindered by resistance to change, particularly among older workers less inclined to learn new technologies. Younger generations, more adept at adopting AI, will likely drive its integration, much like they did during the IT revolution.

Implications for AI’s Future

The slow adoption of AI underscores a broader truth: transformative technologies require time, talent, and societal restructuring to deliver their promised benefits. Companies like Google and Microsoft recognize AI’s potential but face challenges integrating it due to their established structures. New AI-driven firms, led by younger entrepreneurs with an innate understanding of the technology, are likely to emerge as leaders, much like Google and Facebook outpaced Microsoft in the internet era.

In conclusion, while AI’s long-term impact could be profound, its short-term contributions to productivity remain limited. The U.S.’s pessimism about AI reflects legitimate concerns about job displacement and inequality, but history suggests that with time and adaptation, AI could drive a new era of prosperity. For now, society must navigate the transition, balancing optimism with the practical challenges of reorganization.

PC端与移动端:谁更有前途?

在科技快速发展的今天,PC端和移动端的竞争成为人们热议的话题。有人认为移动端因其便携性和普及性更有前途,也有人坚信PC端在专业领域的不可替代性。究竟哪一端更具发展潜力?本文将从两者的优势、市场趋势以及未来发展进行分析。

PC端的优势

PC端凭借其强大的性能和灵活性,在多个领域占据重要地位:

  1. 性能与生产力
    PC的硬件配置远超移动设备,适合运行复杂任务。例如,视频编辑、编程、3D建模等专业工作依赖PC的强大算力。专业软件如AutoCAD、Adobe Photoshop在PC上的体验更流畅,功能更完整。

  2. 多任务处理
    PC的大屏幕和键盘鼠标组合支持高效的多窗口操作。无论是处理复杂表格、编写长篇文档,还是同时运行多个应用程序,PC都能提供卓越的生产力体验。

  3. 可扩展性
    PC硬件易于升级,用户可以更换显卡、增加内存或存储,延长设备寿命。这种灵活性是移动端难以企及的。

  4. 游戏与专业市场
    高端PC游戏和专业工作站(如AI训练、科学计算)对硬件要求极高,移动端短期内难以完全替代。PC游戏玩家和专业用户仍是PC市场的重要支柱。

移动端的优势

移动端以其便携性和广泛的用户基础迅速崛起,成为日常生活中不可或缺的一部分:

  1. 便携性与普及性
    智能手机和平板电脑随身携带,随时随地满足用户需求。根据2024年数据,全球智能手机用户约40亿,远超PC用户。这种广泛的普及性为移动端创造了巨大市场。

  2. 生态与便捷性
    移动端的应用生态高度成熟,涵盖社交、娱乐、购物、轻办公等多个场景。微信、抖音等应用的便捷体验让用户能够快速完成任务,适应快节奏的现代生活。

  3. 技术进步
    移动芯片性能显著提升,例如苹果M系列芯片和高通骁龙8 Gen 3,已能处理部分PC级任务。5G网络和云服务的普及进一步增强了移动端的竞争力,例如云游戏和远程办公的流畅体验。

  4. 市场趋势
    移动端在消费市场表现强劲,尤其是手游行业。2024年全球手游收入约900亿美元,远超PC游戏市场。移动端在新兴市场的增长尤为迅猛,吸引了大量开发者和投资。

前景对比

PC端:稳定但增长有限

PC端在专业领域的地位难以动摇,尤其在设计、科研、游戏开发等场景下,PC仍是首选工具。然而,PC市场的增长趋于平稳,主要面向专业用户和高端消费者,缺乏爆发式增长的潜力。

移动端:商业潜力巨大

移动端凭借便携性和用户基数,在消费市场展现出更大潜力。尤其在娱乐、社交和轻办公领域,移动端占据主导地位。然而,其在复杂任务上的局限性(如大屏操作、硬件扩展)短期内难以完全弥补。

融合趋势

值得注意的是,PC端与移动端的界限正在模糊。云游戏、远程桌面、折叠屏设备等技术让用户可以在不同设备间无缝切换。未来,单一设备的主导地位可能被跨平台协同取代。例如,微软的Windows 365和苹果的生态系统都在推动设备间的深度整合。

结论

移动端在消费市场和普及性上更具“前途”,尤其适合娱乐、社交和轻办公场景。然而,PC端在专业任务和生产力领域仍不可或缺。两者的前景并非零和博弈,而是各有侧重。用户应根据需求选择合适的设备:追求便携和快节奏生活的可选择移动端,而需要高效生产力和复杂任务处理的则更适合PC端。

展望未来,跨设备协同和云技术的发展将进一步打破设备界限。无论是PC端还是移动端,适应用户需求、提供无缝体验的平台将在竞争中脱颖而出。

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