Unable to Send Email?
Frustrating, I know.
In fact, fixing email delivery issues is one of the top three things we do for our server management customers.
You can save yourself some money by checking these five items first.
1. Bad Passwords
Never ASSUME, because when you ASSUME, you make an ASS of U and ME. — Jerry Belson
This sounds simple enough but many support tickets we see turn out to be simple password issues. People complain they cannot send email and assure us the password is correct. We reset the password and bang — email is flowing again.
I think the problem often stems from extra spaces.
Firefox and other applications often add a spaces to copy and pasted passwords. To be certain you are not picking up a space, paste the password to your address or search box in your web browser. This is a quick and easy way to verify you’ve copied the password correctly.
If ever in doubt, just reset your password when testing.
Wrong Authentication Method
- Normal or Plain Password
- Encrypted Password
Most systems support normal/plain as well as encrypted passwords. In most cases, you should see an error about “authentication methods” if this is the problem.
Password encryption and network security (Tip #5) are often confused. In many cases if you are required to use a secure network connection, you want to use a normal or plain password settings. This is not insecure because by using SSL at the network level, then entire transaction is secure.
2. Mail Server (SMTP) is Offline
Sometimes mail servers crash — not often but I see it happen on WHM/cPanel and Plesk servers. Simply restarting the service from the control panel often fixes the issue.
Your email client should return a connection error.
The clue in this message is “mail2.rackaid.com is unknown.”
In this case, there’s a typo in the hostname. Watch carefully for such errors as they are common. If you are certain your hostname is correct, then check for DNS issues.
3. ISP Blocking Port 25
Your ISP is blocking port 25.
This is a common issue on customer support desks. Many ISPs force you to use their own SMTP servers even if you have your own.
U-verse, ATT DSL, and Comcast often block port 25 by default. I even see this on business accounts.
You can test if port 25 is blocked by using a telnet client to connect to port 25. For example:
[jeffh@office ~]$ telnet mail.rackaid.com 25 Trying 220.127.116.11...
This test just sits there until it times out. If I use SSH to connect to my server then test the port, it works. I see the SMTP banner.
'. 220 mail.rackaid.com ESMTP Postfix
If you see the STMP banner, then your ISP (or firewall) is blocking the connection.
One tip is to use port 587. Many ISPs do not block this port:
[jeffh@office ~]$ telnet mail.rackaid.com 587 Trying 18.104.22.168... Connected to mail.rackaid.com. Escape character is '^]'. 220 mail.rackaid.com ESMTP Postfix
If that still fails, call your network provider. On most business accounts, the will permit port 25. Increasingly, residential accounts are permanently blocked.
4. SMTP Authentication
Some email systems use an older authentication method called POP before SMTP. With this method, you only need to configure your IMAP or POP3 settings correctly. When you check your email, the server remembers your IP address and then permits you to send email for a period. Many systems still permit this as an option.
This method works fine until new security policies are put in place that enforce the use of SMTP authentication.
For example, for years Plesk enabled POP before SMTP by default. In more recent versions this is now disabled.
If you encounter this change, email accounts that were able to send may no longer be able to send email.
If you get a relay denied error and your password is correct, then SMTP authentications is likely not correct.
Often, email users with this issue can receive but cannot send email.
5. Connection Security
For security, many email service providers now require you to connect to SMTP over a secure connection. SMTPS or secure SMTP uses SSL to secure the network connection between your email client and the server. I recommend all email communications be sent over SMTPS.
In MS Outlook, you may need to select “This server requires a secure connection.” There’s similar options in other email clients.
In addition to making this setting, some servers may require you to connect on port 465 instead of port 25. Port 465 is reserved for SMTP connections over SSL. If port 25 and port 465 fail, try port 587. Port 587 is the mail submission port.
If these don’t fix your issues, call your email service provider. If you are the email service provider and need help — call us. We provide support for Linux-powered email systems including Postfix, Qmail and Sendmail.
Latest posts by Jeff Huckaby (see all)
- How To Use Linux Screen - July 14, 2014
- How To Limit MySQL Max Connections Per User - June 17, 2014
- 3 Great Ways to Secure the WordPress Login (And 1 to Avoid) - June 6, 2014