Mail 4.5 corrupts PDF attachments from gmail (while outlook 2011 doesnt)

Question

I have a gmail account with scanned documents.
I add this account to in Mail and then some of the PDFs are damaged and can not be corrected. The interesting matter is that via web-access and Outlook 2011 there is not a problem.
I have tried many different solutions I could find on the web incl. here. From deleting the mailboxes to deleting the cache-files. Ultimately I deleted the whole mail app (incl. lib files with CleanMyMac), reinstalling and reinstalling the combo.
After adding the account the last time, I minimized the window, till all activity was finished and everything cashed etc.
I opened mail and again the same problem.
Additional remarks: There are many attachments with the same name, because they were send by a HP Office machine. Some have a problem most don't I would estimate the problem is in 10% of the mails.
Again via Web-access and Outlook 2011 all attachments are correct.
I could use Outlook, their calendar doesn't sync with gmail and I also don't like how outlook is handling (and messing-up) my v.cards .
Any help would be highly appreciated.

Answer 1

Ernie Stamper wrote:
The IMAP setting to Keep copies of messages and their attachments has little impact unless not connected to the internet and wanting to work Offline. If connected to the internet, and you click on a message, it will be downloaded, even if not already so by virtue of this setting. If not selected to Keep copies . . . and attachments, then you will be subject to the goodness of the internet connection at that moment. I am only partially keeping abreast of your investigations, but it may be that transmission is muddled at certain times?
I didn't actually try reading the messages without an internet connection. When I had the account in the default "message+attachment" option, the attachments tended to stay on the server. When I switched to "message, no attachment", the attachments were always downloaded. That sure sounds like the opposite of what I would have expected. I've never used the "message, no attachment" setting so that is new to me.
But I may be missing a step in the sequence of things you have found out. Do you have any reason to think that in the message cache created by selecting Keep copies . . . something could be altering files?
I know that if the Mailbox index gets corrupted, it can cause attachments to be lost - at least temporarily. When I do testing with a local mail server, sometimes the timing is off (too fast maybe) and the message is almost always corrupted. Rebuilding the mailbox fixes it.
My initial theory was that the HP devices were spitting out bad MIME messages and that gmail was fixing them. Now I think that gmail IMAP just flakes out every so often with these big files. There could be other explanations too. The PDF was just truncated. I don't think a bug in Apple Mail is a likely possibility.