Mail keeps disconnecting

Happens to me, too - and has done for about six months. It appeared to get better with the last but one update to the OS, but is back now I'm on 10.8.2. It's very annoying. I thought it was my machine but now I wish I'd contacted Apple within the time for free advice.

I've had this problem since I upgraded to Mountain Lion from Snow Leopard. Something working for me so far today: the SMC Reset here (basically shutting down, unplugging, waiting 15 secs, restarting) seems to have solved the problem. Skip down to "Resetting the System Management Controller (SMC)": http://support.apple.com/kb/HT3964

I realized I changed one more thing before I found success today. I changed my DNS server settings to these (which were recommended by an Apple support tech for another network problem I was having):

208.67.222.222

208.67.220.220

When I later switched back to the default DNS, ( 192.168.2.1 ), and let my Mac go to sleep and then wake up, I had the dreaded !-in-a-triangle symbols again.

Just now I changed the DNS servers and applied them, and the dead mailboxes came alive instantly. Try the 208 servers above. Fingers crossed that this isn't just a temporary fix. WIll update if I have trouble.

Thanks Scott. I'm sure a lot of people are, like me, watching your progress.

W

Still working. Just tested it with automatic sleep, instead of me manually putting my Mini to sleep. Both working.

Apple Tech support just called to see how my Mail app was doing after reinstalling Mountain Lion. (Didn't help.) I told him about my DNS server fix. Dude said he thought I'd already tried changing the DNS, because my case history had me changing my DNS servers. However, that was when I had Snow Leopard, and I didn't change the DNS settings after the upgrade to ML.

Tech support guy asked which DNS servers I was using and he said, "Oh I would have recommended 8.8.8.8 and 8.8.4.4." So maybe try those too.

I confirm scott321's solution!! Thanks Scott, this has been annoying me for a while.

I was having this issue specifically with my Gmail account (which was IMAP).. but I also had an IMAP work account which never had any issues.

However, upon changing the DNS to the Google 8.8.8.8, the Mail app immediately reconnected my Gmail IMAP account removing the triangle/exclamation.

I will test out to see how it handles sleeps over the next few days/week.

Many thanks for the suggestion, seems a bit silly that it is a DNS related issue.

i have to same problem, you are not the only one. ME TOO!!

Scott321's solution worked for me. I use Open DNS (openDNS.com*) and I also have the Google DNS active.

This is what I did:

1 Go to System Preferences (Apple menu > System Preferences).

2 Click on Network (Usually third row down — "Internet and Wireless" — and third icon across)

3 Select the first connection in the list on the left-hand side (usually Wi-Fi or Ethernet) and click Advanced (bottom right of window).

4 The next window has a menu at the top ranging from Wi-Fi to Hardware. Select the tab that says DNS.

5 Note down the numbers you have there (necessary should you wish to revert)

5 Using the + or - buttons (bottom left), delete the existing numbers, and (one at a time) add to the list these numbers:

8.8.8.8

8.8.4.4

208.67.222.222

208.67.220.220

Click OK, then on the next window, click Apply.

If that's not simple enough, there are also instructions here: see "Configure Your Mac's DNS" about halfway down at: http://macs.about.com/od/networking/qt/configure-your-macs-dns.htm

* Open DNS is free to use for home use and also gives flexible parental controls as well as protection against phishing and ID theft. You can simply add the numbers above or, to find out more about Open DNS, go to http://www.opendns.com and click on Home DNS (middle of the way down on right hand side as of 18/03/2013). On the next window click Parental Controls. On the next window click the Open DNS Home tab and sign up.