Mail SMTP servers keep going offline

Many Mail.app users are experiencing an problem in which the application will not send. The Mail application receives incoming messages properly, but when users attempt to send messages they are presented with errors such as "The sender address email@example.com was rejected by the server smtp.example.com." In other cases, the server simply goes offline and will not send messages.

Apple Discussions poster Rodi OLeary writes:

"I have been unable to send .Mac mail for three days. Receiving mail fine. Oddly enough I can send mail from my work computer which is running 10.4 but not my primary home computer 10.5.4. Prior to the outgoing failure I changed no settings myself just did the updates."

This problem appears reside with the Mail application and how the outgoing connection is being handled, not with MTP setup issues such as port number and authentication schemes, since other email applications such as Thunderbird and Entourage seem to work properly with identical settings. Additionally, the problem appears to be machine-specific and not due to some networking error or ISP block of service ports, since users with multiple machines on the same network have Mail working fine one one and not the other.

Jeffrey Habig writes:

"I am having the same problem with my Powerbook (leopard). It seems to be network dependent as I don't have the problem at work - only when I come home (wireless network - cable one). I tried adding the cable one smtp server and it also went offline. My iBook (Tiger) is on the same network and is not having any problems."

In addition to only occurring in certain network environments, this problem seems to be intermittent, with SMTP access working fine some days and then failing at other times. For some users the time between working and not working has been days, whereas for others it goes out for only a few hours. Nothing apparent seems to be the cause of the outage. Regardless, there are various reasons Mail would have problems connecting, including permissions problems, changes to the accounts given the recent switch to MobileMe from .Mac, and Firewall blocks.

Troubleshooting Steps and Fixes Delete the Mail preferences and recreate the accounts For some users, this problem is just a matter of corrupted settings files, and removing them may help. To do this, go to the /username/Library/Preferences/ folder and remove the file com.apple.Mail.plist, then restart the Mail application. When Mail starts, enter one account at a time and test each accordingly. For MobileMe users who were switched from .Mac, set up the accounts with the "username@me.com" address instead of the old "@mac.com" address.

Additionally, it may help to completely clear out all MobileMe accounts and email-related settings and set them back up again, since there is a high probability that this problem is due to updates and settings changes to Mail as part of Apple's MobileMe transition. To do this:

1. Go to Mail's preferences and remove all MobileMe accounts
2. Quit Mail and delete the Mail preferences files (Fix #1 above)
3. Go to the MobileMe system preferences and sign out
4. Sign back in and open Mail, set up the accounts and try again

Lastly, it may be possible a corrupt file in the "Mail" folder itself (/username/Library/Mail/) could be causing the problem, and resetting all accounts completely by both removing the preferences file as well as removing the "Mail" folder could clear the problem. However, it is recommended that users try other fixes before resorting to this working, as it will remove all previously downloaded messages, as well as reset all custom mailboxes and organization.

Reset and repair keychains The authentication information for SMTP servers is stored in the user's keychain, and repairing and resetting the keychain may solve the issue. To do this, open "Keychain Access" (in the Utilities folder) and select "Keychain First Aid" from the "Keychain Access" menu. Enter the account username and password, and click "start" to verify (or select the repair option to fix any problems found during verification). To reset the SMTP entries for the keychain, locate the names of the SMTP servers (they should have a blue "@" symbol next to them), and remove them. Next, open the Mail application and try sending mail again, entering authentication information when prompted.

Turn off the Firewall It is possible this problem could be due to firewall conflicts with MobileMe or other aspects of Mail. If this is the case, then turning off the Firewall could enable proper SMTP connections again. To turn off the Firewall, go to the "Security" system preferences and select the "Firewall" tab. Then select the "Allow all incoming connections" option and retry Mail.

Run a permissions fix on the hard drive and home Library folder Some users have found that their problems were from inaccessibility due to permissions problems in their home directories. To ensure accessibility for files, first run Disk Utility's "Permissions fix" routine on the main hard drive, and then check Mail's functionality. Failing that, run ensure the account has read and write access to all the files in the user library. To do this, run the following commands in the terminal (enter an administrator password when prompted):

• sudo chown -R `id -un` ~/Library
• sudo chmod -R u rw ~/Library

The first command will recursively change the ownership and group of all files in the library folder to that of the current username and groupname of the active user; the second will ensure the owner of the files has both read and write permissions on all files in the library. When these commands have been run, open Mail and ensure all accounts are properly set up, and then attempt to send email again.

Feedback? Late-breakers@macfixit.com.

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