Why can't I send mail from my hotel room?

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I checked in to my hotel which provides free high speed internet. All was well and good, except that after a while, I could no longer send email. I could receive all I wanted, but all my attempts to send failed. And the weird thing is that the next morning, sending mail worked ... for a while. What's going on?

I've run into this as well. It's very strange, but once I understood it, it kinda, sorta, made sense. And understanding it allowed me to work around it.

But it's the kind of thing I wouldn't expect the front desk to be able to help with at all. You're kind of on your own.

And I think you can blame spam.

You may already know, but when you send email, you're connecting to a remote email server, and communicating on a particular "port". Port 25 happens to be the SMTP mail sending port.

Many hotels, and possibly other facilities, are starting to intercept mail being sent to any mail server on port 25, and redirecting it to flow through their own mail server. So even though your mail program is configured to send your mail through the SMTP server of, say, your isp - the hotel's infrastructure sends it through their email server anyway.

And on top of that, they then impose a cap on the amount of email you can send.

Why do they do that? My theory is spam - they don't want some spammer to sit in their hotel and use their resources to send hundreds or thousands of spam emails. Or similarly, have a legitimate guests machine that's infected with a spam-sending zombie to do the same. Not only would it clog the hotel's network, but it could result in the hotel's IP address being added to spam-blocking blacklists. Not something the hotels want.

So they intercept, and limit what you can do.

Fortunately there are several workarounds. And the good news is that the workarounds are difficult for the spammers to exploit.

Here are several ways to address the issue:

• Use web mail. If your ISP has a web interface, than can be a quick way to be able dash off that important email with no further thought.
• Use a proprietary network. The most common example might be AOL - AOL mail seems unaffected by these SMTP hijacking tricks.
• Use a VPN. Similar to the previous point, if you or your corporation have the ability to connect to a VPN, or Virtual Private Network, that connection bypasses these types of redirections.
• If you have access to your mail server's configuration, or your ISP is willing to do so, have the mail server listen on an additional port. For example in addition to waiting for mail on port 25, have it listen to port 26 also. Then configure your client to send using port 26 instead of port 25, and you've bypassed the hijack.
• Use SSH tunneling. If you can, this is my recommended solution. When you're on a foreign network, like a wifi hotspot or even a hotel's hardwired network, you really don't know who else might be sniffing your internet traffic, and possibly eavesdropping on your mail, or worse, your mail passwords. How can I keep my email safe from sniffing? discusses "SSH Tunneling". The nice side effect of this technique, is that it also completely bypasses the hotel's attempts to get in between you and your mail server.

Like I said, I don't really blame the hotels, they're trying to address a very real and serious problem. I do wish that they had better information available about what they're doing, or at least a warning of some sort. But ultimately I blame the spammers and the purveyors of malware that have forced the hotels and others into the position of having to take these types of actions.

Related:

• Ask Leo! - How can I keep my email safe from sniffing?

• Ask Leo! - Can hackers see data going to and from my computer?

• Ask Leo! - What is POP? Or POP3? Or a POP account? And what about SMTP?

Article 9536 | Posted December 19, 2005