Odd Corruption in IMAP attachments
A poster on the Apple Discussion Boards is having a very weird experience 
with attachments in his IMAP account.
Dylan Muir finds that when he views large attachments stored on his IMAP server in Mail.app, they are corrupted. If he views them in a webmail client, they aren’t. If he views them in Thunderbird, they aren’t. It’s only Mail.app.
Unusually, the Apple Mail gods on the Discussion Boards seem to be out of ideas.
I wonder if anyone here has experienced this too (I never have), and knows what’s going on.
Tags: Apple Mail, attachments, bug, corruption, imap, mai.appRelated posts
October 12th, 2006 at 10:46 pm
It has happened to me before, but isn’t always reliable. The thing I hate most about mail at the moment is it refuses to cache certain emails on my IMAP service - they always seem to be from the same sender.
Another drama I’ve had is Mail blithely ignores certain unread messages, and no amount of mailbox rebuilds seem to fix it! Looking forward to leopard…
October 12th, 2006 at 10:58 pm
I recall someone talking about something that reminds me of this problem on the Cyrus-IMAP mailing list, which I would have been looking at in January 2006 timeframe. The messages may have been from previous months though. I think the person had or was planning on reporting the issue to Apple. Hope that helps!
October 12th, 2006 at 11:43 pm
Well remembered! It was kind of you to post in the Apple Discussions too.
I was secretly hoping that some fix would emerge. I get grumpy at the thought that Thunderbird can do things Mail.app can’t :)
October 13th, 2006 at 2:18 am
You say the attachment appears to be corrupt if he views the attachments on the server. So what if he views them locally - say by dragging and dropping the mail to a local mailbox in Mail?
As I understand it, with remotely-held mail the server is supposed to be responsible for MIME-type handling, but some clients “cheat” and do that themselves. (I may have misremembered this, but if I have doubtless someone who knows more about IMAP will correct me.) And I too have come across an account of something like this with Mulberry: again the problem wasn’t encountered in Thunderbird, but then that was merely because Thunderbird was breaking the IMAP standards and doing what it shouldn’t.
IOW, it may be the server that is at fault here not Mail at all.
October 13th, 2006 at 5:43 am
I had this problem with a provider called GMX.
What helped was to delete all existing emails and start from the scratch. Of course, this isn’t the solution to someone who has important emails and everything in his/her imap account.
I don’t know how the problem got fixed in the end. I somehow had given up on using apple mail. and one day, I tried again and voila. Everything worked.
Wish you good luck. Play around with the Server/Network settings in Mail. That might help somehow.
October 25th, 2006 at 8:26 pm
I am currently dealing with this problem in my office. In our case, the problem only surfaces when there are MULTIPLE attachments. Messages with a single attachment are always fine. With multiple, one or more will be corrupt. And as mentioned earlier, if you download from the webmail account they are fine. At first I thought it was Symantec Antivirus, but I was proved wrong
November 11th, 2006 at 3:02 am
I have the same problem discussed in that thread. I also agree with Joe in that its only an issue when there are multiple attachments. I’ve tried all of the suggestions in the apple support thread and still find that the images are corrupt… often in different places. For the record, they show up flawlessly in thunderbird, pine, webmail, etc.
December 3rd, 2007 at 12:03 am
The problem persists in Leopard’s Mail.app (version of Nov 2007).
One single attachment almost ever downloads correctly. It sometimes (but seldom) fails, if it’s really large. But multiple attachments almost never download correctly here, especially, if the attachments are displayed inside the mail text or are opened before downloaded completely.
What can we do? That renders mail.app pretty useless to me, but I don’t want to switch to thunderbird (I don’t like thunderbird)
December 3rd, 2007 at 11:31 am
I have the same problem. Entourage seems to work fine but it is telling me that that the IMAP server is not sending down the attachment. Entourage offers me the ability to download the attachment. I have to manually select the option. I sure wish Mac Mail worked, but there seems to be no client side option for caching attachments.
July 9th, 2008 at 6:45 am
Hi, I had the same problem with a Mail with two attachments on Leopard. And I had the same problem with an HTML Mail with an embedded image (which makes two mime-encoded parts). Strangely, it worked when the Mail arrived, i.e. I could see the HTML content. After I opened the Mail in Thunderbird once it no longer worked. I am not sure if this is just a coincidence, but maybe Thunderbird stores something in the IMAP folder that Mail.app doesn’t like?
Interestingly, I can see the mails and attachments with my iPod Touch. I wonder why this issue isn’t yet fixed at least in Leopard.