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 … again, for a while. What’s
I’ve run into this as well. It’s very strange and even frustrating,
but once I understood it, it began to make sense.
And understanding it also allowed me to work around it.
But it’s the kind of thing that I wouldn’t expect the front desk to be able to
help with at all. You and I? We’re kind of on our own.
The root cause of all this?
SMTP is an acronym for Simple Mail Transfer Protocol which is the protocol used to transport email messages from computer to computer until they reach their destination. SMTP is used … continue reading.
From the Ask Leo! Glossary
You may already know, but when you send email your desktop email program connects to a remote email server, and communicates on a particular “port”.
Port 25 happens to be the default SMTP mail sending port. It’s used not only to send email from your computer to the email server that you use, but also between email servers as they deliver email all across the internet.
Hotels and Port 25
Many hotels (I’ll use the term to refer not only to hotels but also any place that provides internet connectivity for free or for a fee) are intercepting mail being sent to any mail server on port 25. Instead of connecting to the server your email program requests, they intercept and connect to their email server instead.
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.
And now that they’re controlling it they then often impose a cap on the amount of email you can send.
Reasons for Interception
Naturally the first reaction is to wonder why in heaven’s name would a hotel, or any one for that matter, want to intercept and limit the amount of email I can send? Isn’t that my business?
Well, yes and no.
Email you send while you’re at the hotel could possibly be traced back to the hotel and even cause the hotels internet connection to be blacklisted.
If you are a spammer, or your machine is infected with a spam-sending zombie, sending unrestricted email that originates from the hotel’s IP address some anti-spam technologies will eventually blacklist the source – the IP address of the hotel.
If that happens you, the other hotel guests and perhaps even the hotel staff themselves may be able to send all the email you want, only to have it be filtered as spam and never reach its destination.
By limiting the number of emails you can send per day the hotel effectively restricts your ability to be a spammer, and dramatically reduces the possibility that their network could be accused of being a source of spam.
There are workarounds.
And yes, the spammers can use some of these as well, should they be so motivated. However even by blocking the default case hotels can at least make a signficant dent in the problem.
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 an alternate port. If your email provider supports this, you may be able to configure your email client to connect via a port other than 25. If they provide an SMTP over SSL connection (more and more common these days) that’s often via port 465 or 587. Being SSL they are significantly more difficult to intercept and thus typically left alone. Your ISP may also provide traditional SMTP access over an alternate port such as 26. The good news about either choice is that things should continue to work when you get back home without having to “undo” anything.
Use SSH tunneling. This gets pretty geeky, and requires an ISP willing to grant you SSH access, but also bypasses all port 25 intercepts.
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.
About that Internet Connection…
One final thought about that internet connection that’s being provided to you.
On top of that, depending on how the network is configured even connections “nearby” your wired internet connection may also be able to see your data passing by, exactly like an open WiFi hotspot.
(This is an update to an article originally published December 19, 2005.)