Almost all mail client program send e-mail using port 25, which is also the port used by mail servers to talk to each other. But port 25 is widely abused by malware to spread worms and spam. As a result, many ISPs are restricting its use.
Hang on – it will make sense in a second:
Most people having a setup where they are on an Internet Service Provider (ISP) like ATT and have an email address like “MyEmail@ATT.net” You connect to the internet using ATT and send mail through the ATT server – no problem.
But if you have your own domain email address or an email address from another ISP you may hit a snag. In these cases you are connecting to the internet through your ISP (like Comcast, SpeakEasy, ATT, etc) and trying to send email through your third party host like “MyEmail@SuperCoolWebsite.com”
Your ISP says “Hey! There is someone on my network trying to send email through someone elses address! This might be spam or malware!” You can receive mail, but you can’t send mail.
Recently ATT and Verizon both made changes that affected outgoing mail. Here’s the fix:
If you cannot SEND MAIL
- Open OUTLOOK
- Select TOOLS
- Select ACCOUNT SETTINGS
- Highlight the account in question and select CHANGE
- Select MORE SETTINGS
- Select ADVANCED
- Change from PORT 25 to PORT 587
- Save everything and restart Outlook

Other email programs will have similar settings. Look for PROPERTIES or PREFERENCES and find the outgoing mail server option.
One other option to check is that you are authenticating before sending. In other words. logging in with your username and password to both check and send email.
In Outlook the options window looks like this:

This tells Outlook to send your username and password before trying to send mail. If you have problems try enabling or disabling this setting.
The screen shots used in this how-to are my actual settings and they work just fine with SpeakEasy and ATT.

(13 votes, average: 5.92 out of 6)










































April 19th, 2009 at 11:45 am
Wow where did you get this info from. It works, but those people from ATT who aren't even in this country keep on telling me to use 465 which doesn't work. Thanks again.
May 16th, 2009 at 5:46 am
Thanks for the quick reference! I'd found a site with this information some time ago, but did not bookmark it. I appreciate the screenshot, and enjoyed your explanation of the issue!
October 3rd, 2009 at 7:41 am
Many thanks for this post Daniel. It helped resolve an email problem that was causing me some frustration. Easy when you know how!
January 9th, 2010 at 3:13 am
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February 4th, 2010 at 10:44 pm
Thanks a ton! ATT couldn't even figure it out.
February 26th, 2010 at 3:13 pm
Thanks a lot! Comcast was of no help a all (big surprise)
March 8th, 2010 at 12:07 am
Thanks so so much..
June 27th, 2010 at 5:21 pm
Thank you sooooooooooooooooooooooooo much ! It worked.
July 21st, 2010 at 5:08 am
my outlook receave but not send mails
incoming mail (pop3)is 202.138.97.97
outgoing smtp is 202.138.96.26
& this same settings work proper in other pc
but not wirk in default pc………………