At a hotel which blocks port 25. Of course, there is no way to find their SMTP server to send email. The solution is that many mail servers also accept mail on port 26, so you either have to find the SMTP server that works on the network (good luck). Or reconfigure your client to use Port 26. On and also, port 26 works fine, so you have to go to the Mail/Preferences/Accounts/Outgoing SMTP Server and click on the combo box and select Edit Server List then click on the STMP server and the Advanced pane. Choose use custom port and type in 26. I normally also turn off SSL to make sure it basically works.

Port 25 Blocking

Many ISPs are blocking what is called “Port 25” which is the port used to send e-mail. They are doing this to cut down on the amount of spam that is sent from their networks.

All e-mail sent via the Internet is routed through the port 25, the channel used for communication between an e-mail client and an e-mail server. Even though port 25 blocking will probably become an industry standard, however, the filter can create problems for e-mail servers and block legitimate e-mail as well as spam.

Port 25 blocking allows ISPs to block spam sent out through their networks, but it tends to punish the innocent that have a need to send through e-mail servers other than those belonging to their ISP. The ISPs that block port 25 require their SMTP server to be used instead of the remote SMTP server or a SMTP server running on your computer.

7 responses to “Port 25 blocking….argh”

  1. pjdavis Avatar

    A little more about this: ISPs, including hotel ISPs, block port 25 bcs. it can be used for both basic SMTP and SMTPAuth, the authenticated variation on SMTP.

    They don’t need to block port 587 bcs. basic SMTP does not use 587.

    A great solution is to use an email vendor that supports SMTPAuth on port 587.

  2. ksg Avatar

    Gmail and the other web-based services are perfect for some people, but not for all. Some organizations (for privacy/accountability reasons) prohibit the use of Gmail because they cannot allow their email to be stored on Google’s servers. Many law firms are in this position, but also many private companies. And for many people, the dreaded “on behalf of problem” gets in the way.

    1. rich Avatar

      Good point Ken. For many folks, “cloud” will never work, but for lots of folks it is so much more convenient. So life will be a balance.

  3. brettm Avatar

    how come you are using an old-school mail client anyway? shouldn’t you be using gmail or some other web-mail? port 80 is always open 🙂

    1. rich Avatar

      Well, if the calendar in gcal was any good, I probably would and if offline worked. But of course all that was probably fixed in the last release of gmail 🙂

  4. ksg Avatar

    If you’ll permit a commercial, I work for Loa Corporation, which makes Loa PowerTools. LPT offers another, more general, solution. And for casual travelers, the free version is usually enough.

    1. rich Avatar

      Thanks Ken, anything to help with this terrible problem.

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