Knowledgebase: Email
Able to receive email but unable to send email
Posted by Bill Williams on 09 August 2008 09:04 AM
 Symptom: You are able to receive email through your hosted email account but you are unable to send email. You may receive an error message from your email client indicating that it is unable to connect to the host server, also you may receive Non-Delivery Report (NDR) emails stating that the server is unable to relay your message.

Cause: Your Internet Service Provider (ISP) is blocking outgoing connections on TCP port 25 (SMTP) any servers other than their own internal SMTP server. This is done by some ISP's in an attempt to limit the spread of certain virus programs that spread by sending out email messages from infected computers using TCP port 25.

How to Confirm: The simplest way to confirm that your ISP is blocking outgoing connections on TCP port 25 is to attempt to connect to your hosted email server via a terminal emulation program such as Telnet on TCP port 25. On windows systems this is done by performing the following:

1. Click Start, then click on Run.
2. In the Run dialog box type: cmd
Then press OK.
3. A black command prompt window should open, on Windows XP computers the title of the window is typically C:\WINDOWS\system32\cmd.exe
4. In the command prompt window type: telnet mail.yourdomainname.com 25
Then press Enter. Note: replace yourdomainname.com with your domain that is hosted on our systems.
5. If your ISP is not blocking outgoing connections on TCP port 25 you should receive a response on your screen similar to:

220-servername.com ESMTP Exim 4.52 #1 Fri, 27 Oct 2006 4:50 -0600
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.

or

220 mail.servername.com

6. If your ISP is blocking outgoing connections on TCP port 25 you will see an error similar to:

Connect to mail.yourdomainname.com...Could not open connection to the host, on port 25: Connect failed


Resolution: You have two options.

Either contact your Internet Service Provider and obtain the host name of the outgoing SMTP server you need to use to send email. You will then need to enter this hostname into the SMTP server field of your mail client, for Microsoft Outlook this is done under the Server Information section of the Account Settings configuration page, you will need to enter the host name your ISP provides for their Outgoing SMTP server in the Outgoing mail server (SMTP): field. You may also need to enter login information for the SMTP server on the More Settings page

or

Change the smtp port in your email client to 26. While the default smtp port is 25 and your ISP maybe blocking it, we have also enable port 36 to do the job and you ISP maynot be blocking it.
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