I had an irritating problem with my preferred OSX mail client, the venerable Mulberry, whereby it would not open the INBOX on my tuffmail.com hosted account but it would open the INBOXs for other mail accounts. It was also quite happy to permit access to other mailboxes in the Tuffmail account.
I could get to that INBOX from other IMAP clients running on Android (K9 Mail) and Tuffmail’s own HTTP clients. It could also be accessed via the OSX Mail App (after a very, very long wait for synchronisation…).
Protocol logging showed the IMAP login and facilities of the mail server, then a SEARCH UNSEEN, then nothing.
I thought there was possibly a INBOX size limit at the provider (though it was nowhere near as big as it has been in the past, and other mail clients worked) or that some bad email was causing Mulberry to bomb the account (but protocol logging showed nothing).
Then I realised that I had installed AVAST on my Mac and that has a Mail Shield component that sits in line with the IMAP connection. I realised this when I saw the certificate pop up in Mulberry from AVAST after restarting the mail client.
Avast Mail Shield gets in the way but only when you restart the Mulberry application. If you didn’t close Mulberry and restart it after the AVAST installation, it might be some days/weeks before you notice any issue. This happens regardless of whether you have SSL on or off to your mail account. It happens regardless of whether you set Avast Mail Shield to scan secured connections except that if you set SSL/IMAPS access to your account and you switch off Avast Mail Shield secured scanning, you can get access.
So I had a decision to make:
1) Don’t run AVAST, but that isn’t very palatable. There are lots of infected attachments and although they might not target OSX, that is going to happen.
2) Use SSL to access your mail account and switch off Scan Secured Connections, but then your other SSL secured accounts are not scanned.
3) Use the Ignore Mail Server option to exclude only the failing mail account and then decide whether you want to do SSL or not to that and the other mail servers. Obviously having SSL on means that your mail is encrypted in transit between the mail server and the mail client, so it is a sensible option to have switched on.
By the way, switching to OSX Mail App with AVAST did show up at least 90+ emails sitting in mailboxes with infected attachments, so even though they were Windows specific issues, at least I got something for my pain. It also shows that you shouldn’t just rely on your ISPs to spot every rogue email.