Have you ever pressed the "Get Mail" button in your email client and received an error stating that it can not connect to the mail server and you should contact your network administrator for assistance? It's a fairly common problem with email and can be caused by many different things. For example, your virus scanner may be blocking the connection, your router may be acting up, your ISP may have a temporary outage, the mail server may actually be down, or you could have DNS issues. On those occasions that you need to do a quick test to verify if your mail server is accepting connections, for sending or receiving email, use TELNET to verify connectivity.
First, for those that are not familiar, SMTP is for sending and POP3/IMAP is for receiving. The telnet command in Windows, MAC, or Linux provides an extremely easy way to verify connectivity to these email services and for that matter many other servers that accept telnet connections. Here's a couple of examples of how to use telnet to test connectivity to your mail server.
Before using telnet you'll need to know what your email client uses as a host for SMTP and/or POP3/IMAP. This is usually located in the email clients account configuration. We will use mail.domain.com as an example.
Open a DOS/Terminal window (Windows = Start - Run - CMD, MAC = Applications - Utilities - Terminal).
Type the following to connect to the SMTP service. The default port is 25.
telnet mail.domain.com 25
If the SMTP server is accepting connections you should receive a greeting from the mail server, something similar to this.
220 mail.domain.com ESMTP MailServer v1.0 Ready
Type 'quit', without the single quotes, to quit the SMTP session.
Now to test the POP3 connection. The default port is 110. Type the following in the DOS/Terminal window.
telnet mail.domain.com 110
If POP3 is accepting connections you should get this type of response.
+OK mail.domain.com MailServer. v1.0 POP3 Ready
Type 'quit' to exit the POP3 session.
And to test IMAP, default port is 143.
telnet mail.domain.com 143
* OK MailServer.v1.0 IMAP4rev1 Ready
Type '001 logout' to quit the IMAP session.
That's basically it. Telnet is a very useful tool that can quickly help you determine if you can or can not connect to your mail server.
First, for those that are not familiar, SMTP is for sending and POP3/IMAP is for receiving. The telnet command in Windows, MAC, or Linux provides an extremely easy way to verify connectivity to these email services and for that matter many other servers that accept telnet connections. Here's a couple of examples of how to use telnet to test connectivity to your mail server.
Before using telnet you'll need to know what your email client uses as a host for SMTP and/or POP3/IMAP. This is usually located in the email clients account configuration. We will use mail.domain.com as an example.
Open a DOS/Terminal window (Windows = Start - Run - CMD, MAC = Applications - Utilities - Terminal).
Type the following to connect to the SMTP service. The default port is 25.
telnet mail.domain.com 25
If the SMTP server is accepting connections you should receive a greeting from the mail server, something similar to this.
220 mail.domain.com ESMTP MailServer v1.0 Ready
Type 'quit', without the single quotes, to quit the SMTP session.
Now to test the POP3 connection. The default port is 110. Type the following in the DOS/Terminal window.
telnet mail.domain.com 110
If POP3 is accepting connections you should get this type of response.
+OK mail.domain.com MailServer. v1.0 POP3 Ready
Type 'quit' to exit the POP3 session.
And to test IMAP, default port is 143.
telnet mail.domain.com 143
* OK MailServer.v1.0 IMAP4rev1 Ready
Type '001 logout' to quit the IMAP session.
That's basically it. Telnet is a very useful tool that can quickly help you determine if you can or can not connect to your mail server.
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