Summary: Mail Shield may conflict with Mailbox Rebuilding.
I've been receiving and sending emails on Mail.app normally using the Mail Shield, I have two IMAP accounts (one is Gmail, the other a private server) and one POP, just recently I noticed while accessing one of my accounts, IMAP, on the iPad (using the native Mail app) that one mail in particular (IMAP, private server) had not been received on Mail.app on my laptop, after trying to synchronize, closing and opening Mail. app I decided to Rebuild the mailboxes, which worked, after the process ended, I noticed there were still some emails missing, but now these were the last emails I had sent (sent folders) on both IMAP accounts (both the Gmail one and the private server one). I had tried quitting mail.app and opening again, synchronizing, taking offline and online again.
This situation kept going for days, until I decided to quit Mail, turn off the Mail Shield, start Mail.app, only then did Mail.app correctly synchronized, and the emails I was missing in my sent folders (which I knew were there from webmail), were finally restored.
So, for some reason, there appears to be some sort of conflict with mail shield and mailbox rebuilding, this is not related to certificates because some mails do get thru, I suspect there's some sort of caching that needs to be purged? Also, there is absolutely no reason to block these emails in particular, some are only text, and I'm 100% positive they don't contain any malware (and they were in the computer prior to the mailbox rebuilding).
Specs: OS X 10.9, Avast! Free AV 8.0 (40005)
