Hi all
I am having a similar problem and its only happened after upgrading to Mountain Lion. When using Lion, I had no issues with mail reconnecting after sleep mode.
Basically when I disconnect from the Wifi and then reconnect, I can't get Apple Mail to reconnect to my email accounts. In terms of disconnecting from the Wifi, it is like after I lock my computer and it goes to sleep etc.
In Apple Mail, there are exclamation marks next to my 4 mail account (all my mail accounts are hosted on Gmail using IMAP). Before upgrading to Mountain Lion, I would just press the "Get Mail" button and it would reconnect and check for emails. But after the upgrade, pressing the "Get Mail" button does nothing at all, right clicking the mail account and "synchronise" or "take online" doesnt do anything, double clicking the exclamation mark does nothing etc.
The only thing that allows me to get the emails checking is restarting the Apple Mail program and things work fine... until it goes back to sleep...
Any ideas?
Thanks!
O