I believe that I have stumbled upon a bug in Mountain Lion mail. Here is the set up:
Mac OS X Mountain Lion Server 10.8.2 running IMAP email service
An assortment of Macs all running Mac OS X Mountain Lion 10.8.2 using Mail as the mail client over IMAP.
Ever since upgrading all company Macs to Mountain Lion we have recieved complaints from people that email attachments are occationaly becoming currupted once moved to other mailboxes such as the Trash or even other IMAP folders. The symptom has not been observed to occur with other mail services such as gMail or iCloud but rather seems to be isolated to how Mountain Lion Mail handles moved emails with attachments on an IMAP service hosted on Mountain Lion server. The issue also seems to be related to PDF attachments only. We could not get the issue to reoccur with say a Pages document. The issue also does not always occur but occurs about 90% of the time.
The email essentially goes from looking normal in the inbox to containing this text in it after it has been moved to another mailbox (obviously the real thing is like a hundred pages long):
Now if that same email, now moved into a new mailbox, apearing corupted to the Mac Mail client, is viewed from say an iPhone or iPad, the attachment appears normal. If a new Mac client is set up to read that email account that email also appears normal. This would indicate that issue does not seem to be occuring server side but however seems related to a cashe issue with the Mail client.
Now this is not a good fix but deleting the entire /User/Library/Mail folder and forcing Mail to completely reconnect to the IMAP server and redownload all headers and attachements fixes the issue. However this only fixes the emails that once appeard corrupted to the client. Any new emails moved around will continue to get corupted. Syncronizing the mailbox does nothing to rectify the issue.
Plee for help:
Obviosuly this is a serious issue and must be rectified. We are using the most standard and Mac friendly/default set up possible (even a Mac server). Has anyone expereinced this issue or want to venture a guess on how to fix it? Does it seem like a bug in the Mail client to you? Any ideas???
I really apprecaite the help.