Sendmail Alternate Port

Sendmail is responsible for sending and receiving e-mail in your VPS account via the SMTP protocol. Installing this application will allow you to send e-mail through port 2525, which is useful if your ISP has blocked you from using port 25, the default port.

Installing Setup Sendmail on an Alternate Port

For installation instructions, please click here.

Why Would I Need to Install This Site Application?

Some Internet service providers (ISPs) have recently started blocking the standard sendmail port (25) to help prevent direct to MX spamming, and abuse of open proxies/relays from their dialup and broadband clients.

Unfortunately, a side-effect of this practice is that it prevents users from accessing our SMTP servers. If you are getting error messages when you try sending mail which state something to the effect that is not responding or not found, contact your ISP to find out whether they are blocking port 25. If they are, you can probably send outgoing mail through their outgoing mail servers (contact your ISP to find out what outgoing mail servers you need to use).

However, sometimes an ISP will not allow e-mail to be sent through their SMTP server with a different domain. In other words, you can only use their SMT server if you have your reply address set to your ISP based e-mail address, not your custom domain name address. If this is the case, installing this site application, and configuring your e-mail client to use the alternate port will allow you to use your own custom domain name e-mail addresses.

Some ISPs Known to Block Port 25

Below is a list of some of the major ISPs that are known to block port 25. While this list is a good starting point, it is far from complete and is prone to change over time. Ultimately, the most reliable way of knowing whether your ISP is blocking port 25 is to contact them directly and ask. You can also use the How to Check if your ISP blocks SMTP guide found at the bottom of this page.

AT&T Global
Bell Internet High Speed (Canada)
Bell south
Charter Communications
Cinncinnati Bell/Fuse Dial-up /east / central
Cox;; (either of the three depending on your location).
OOL (Optimum Online)
Pacific Bell (Pacbell)
Road Runner (NYC) (if outside the NYC area, please call your local Road Runner Support team)
Rogers Hi-Speed
SBC Yahoo
Verizon or

How to Check if your ISP blocks SMTP

Windows Users

  1. Click Start from your Windows Taskbar.
  2. Click Run... from the Windows Start menu.
  3. Type telnet 25 into the Run... dialogue box.
  4. Press Enter or Return.

Mac Users

  1. Launch Terminal.
  2. At the $ sign prompt, type telnet 25.
  3. Press Enter or Return.

Linux Users

  1. At the command line prompt, type telnet 25
  2. Press Enter or Return.

if you get back 220 . . . your ISP DOES NOT block port 25.

If your connection hangs, fails, or returns something other than then your ISP IS blocking or redirecting port 25 to their own server.

Configuring your Mail Client to Use an Alternate Port

Once you have installed this site application, you will need to configure your e-mail client to use the new alternate port. Below are some basic instructions on how to do this on a variety of popular e-mail clients, if your specific program is not listed below, you will need to contact the author of your e-mail client for specific instructions on configuring an alternate SMTP port.

Microsoft Outlook Express

  1. Click Tools -> Accounts from the top menu bar.
  2. Select your e-mail account from the list and click Properties.
  3. Click the Advanced tab from the top.
  4. Change the Outgoing mail (SMTP) to 2525.
  5. Click OK.

Microsoft Outlook 2007

  1. Click Tools -> Account Settings from the top bar.
  2. Select your e-mail account from the list and click Change.
  3. Click the Advanced tab from the top.
  4. Change the Outgoing server (SMTP) to 2525.
  5. Click OK.

Microsoft Outlook 2003

  1. Click Tools -> Email Accounts from the top menu bar.
  2. Select View or Change existing e-mail accounts from the options and click Next.
  3. Select the account having problems and click Change.
  4. Click on More Settings.
  5. Click on the Advanced tab.
  6. Change Outgoing Mail Server (SMTP) to 2525.
  7. Click Okay.
  8. Click Next.
  9. Click Finish.

Mozilla Thunderbird

  1. Click Tools -> Account Settings from the top menu bar.
  2. In the left side, click on Outgoing Server (SMTP).
  3. On the right side, click on the Edit button for your e-mail account.
  4. Change port to 2525.
  5. Click Okay.
  6. Click Okay again.