Unable to Send Email? Check These 5 Things

send email error

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

Password authentication security and network security are different settings. They both must be correct.
If your password fails after resetting, make sure you are using a valid authentication method.  Most email clients support a variety of authentication methods such as:

  • Normal or Plain Password
  • Encrypted Password
  • Kerberos

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.

cannot send email

Thunderbird error due to an incorrect hostname.

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

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
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.

Server rejects the email with relay denied. This likely means SMTP authentication is not enabled.

Server rejects the email with relay denied. This likely means SMTP authentication is not enabled.

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.  


Getting Help

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.

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Jeff is the CEO and founder of rackAID. He has been working in hosting industry since the days of Rackshack's famed customer appreciation parties back in the early 2000's. Jeff is an avid cyclist, wine enthusiast, and admitted Kraftwerk listener (please don't hold that against him). You may spot him at any number of hosting, startup and small business conferences


  • Patricia Jones January 17, 2010 at 1:06 am

    How do I restart the pop3/imap

  • Patricia Jones January 17, 2010 at 1:07 am

    How do I find email sent to my account that where not received?

  • FRANCES DUFF February 10, 2010 at 12:23 pm


  • Jeff H. September 19, 2010 at 10:38 am

    If you are talking about restarting a pop3/imap server, the method will depend on your server.  For desktop clients, typically they will check email again on open.

    If someone sent you and email and you did not receive it, the sender should have received a bounce.  There is no way for you to retrieve this email without contacting the sender and having them send it again by alternate means.

  • Jeff H. September 19, 2010 at 10:39 am

    Some email clients will not show images. So this could be an issue with your friend’s email system. If you are embedding them directly into your email, try sending them as attachments that sometimes will help.

  • Glenda Boyd September 18, 2010 at 7:40 am

    My problem is the same as the one posted by Francis Duff 02/10/2010


  • Harry Henson September 23, 2010 at 9:54 am

    As a novice I do not understand how to proceed. When tryingto send e mails I get a message including “port25 blocked” What can I do?Lemon

  • Jeff H. September 23, 2010 at 12:00 pm

    Port 25 blocked likely means your ISP is blocking your connection to your server.  Some servers support port 587.  In your email client, see if you can set the outbound SMTP port to 587.  If this fails, I would call your ISP for further assistance.

  • stephen hoolahan November 7, 2010 at 11:50 am

    i am recieving emails about possible employmentn and i am unable to reply why is this

  • Lydia Parker February 24, 2011 at 12:39 pm

    I can receive emails but unable to send emails

  • Jeff H. March 8, 2011 at 9:14 am

    @Helen Poe
    From you description, you do appear to have an local computer issue and not a server level issue.  Since one computer works and the other does not, this suggests and issue with your desktop.  Perhaps a virus that is not detected, incorrect settings, or something blocking access. 

    If you cannot resolve this on your own, I suggest getting support to look into it.  Best Buy, Staples or online services like http://www.iyogi.com/ provide desktop support.

  • Helen Poe March 7, 2011 at 10:45 am

    My server is casscomm.com. I can send emails from my laptop, but I cannot from my desktop. I have the same settings on both computers. I find it strange that if I use pop3 and 110 that my internet server Firefox or internet explorer will not work, I have to turn off my pop3. Why is this? My internet provider said that there is nothing wrong with my connection he can’t figure it out. He says my computer is not working right, I/ve run Malware and antivirsus and there is no problem there. I also ran a test on the computer and it said the variables are ok. what now?

  • B. Hayes March 11, 2011 at 2:11 am

    I’m trying to send a long list blind copy with a link to a theater site….I keep getting messge “temorarily unable to send, try later..”  this started last night and persists this morngin…what do I do? thanks

  • Nina May 8, 2011 at 10:42 am

    I’ve spent 3 lon sessions with Dell after a virus.  But, when I try and send e-mail to more than one person, a box pops up that says Unable to send message because of error”..I can send e-mail..and forward. Any ideas welcomed!

  • Ron May 18, 2011 at 6:55 am

    Why am I unable to send emails to members of Match.com?

  • Jeffrey Huckaby May 23, 2011 at 9:26 am

    @Ron You could be blocked at Match.com. I would contact your ISP or Match.com through another means.

    Perhaps your email service provider is blocking emails with multiple recipients.  I would contact them. For malware, I use http://www.malwarebytes.org/

    @B Hayes
    Most likely your email client and/or your ISP is blocking long BCC’s. That tactic is often used by spammers.  Consider using a mailing list service if you are sending to more than 10 recipients at once.  MailChimp is easy to use and cheap.

  • Eh? June 27, 2011 at 8:09 am

    Every time I try to send an email I get a message saying “to continue sending messages please sign into your windows live hotmail account http://mail.live.com after you sign in will show you a picture and ask you which letters and numbers you see in it. This helps us prevent automated programs from sending junk.” I did what it told me to do but I still can’t send emails? What do I do??

  • liz robertson September 13, 2011 at 1:59 am

    please help me with my email i cnt get my email send lout for a few weeks now. Please help asap.Thank You. LIZ.

  • Jeffrey Huckaby September 14, 2011 at 8:34 am

    Our focus is on email servers. For desktop support, start with your internet provider.  Call them and see if they can help.  If that still fails, then you may need to hire a desktop support company. There are companies now that for a flat fee will login remotely to your desktop and fix your issue.

  • cherry September 28, 2011 at 4:10 am

    Unable to send email address with capitals?

  • Free pdf editor download October 12, 2011 at 7:38 am

    Well that never happened to me yet but it’s always great to know information of this kind. Many thanks for this article!

  • Tom Hensley November 9, 2011 at 1:08 am

    I have verizon.net.  I am not able to send or receive email.  I get this error, 0x800ccc0d .  What can I do?  The verizon techs never want to address this situation.  They want to always make sure I’m using Verizion.net, (their email).  I have Windows Live, Hotmail, Thunderbird mail and none of them will work until I get the error, 0x800CCC0D, fixed.  What can I do?
      Is there software anywhere that will fix any email error?

    Thank you,
    Tom Hensley

  • mp4 to mp3 January 10, 2012 at 5:27 am

    Why can’t I send a mail to a person with capitals in the email address?

  • doreen January 16, 2012 at 7:38 am

    why can,t i dleat my email, and how to make the email smaller

  • nike free run sale February 28, 2012 at 9:45 am

    I use foxmail to send and receive email, it’s very ok!

  • Efrain Vicente Garcia February 28, 2012 at 9:00 am

    I’ve lost my email connection and wish
    I could get it back. I have been tryinmg everything to recover it. E.V.Garcia

  • carol shugart March 9, 2012 at 6:36 am

    i receive e-mail but unable to read it and unable to send mail

  • fred stidham March 17, 2012 at 7:08 am

    if my incredimail is receiving mail i dont see it

  • ed March 19, 2012 at 10:13 am

    I get an error message that pass word is rejected.

    This system is years in the running, not new, and when I reenter my pass word, it is rejected again. I have three e mail addresses and all three has the same error.

    What to do.

  • earl April 26, 2012 at 4:53 am

    when i push the “send” it says “error please try again now this has bee goin on for 3 weeks i have a dell labtop latitude d610 i use comcast for my internet

  • megan cook May 8, 2012 at 12:00 pm

    My computer can receive emails but not send them