Ongoing IMAP sync with users migrated to Apple El Captain (Apple Mail) producing tons of traffic

Problem reported by Norman Roy - 11/4/2015 at 3:15 AM

Submitted

Hello,

for some days we had massive problems with Apple Users who migrated to El Captain, using Apple Mail.

IMAP sync was was running all the time, blocking the whole system.

At the server we could see massive filetransfer (50-70 Mbit per user) in the background.

Update 14.4.5784 fixed the issue that the users can´t work anymore, but still massive data transfer is running in the background. Though the problems got better after the update, we think that it concerns the RFC change in the fix.

Somehow there might be a reference with: the Topic "upgrade to 14.4.5784 IMAP folders not re-syncing"

Other users/accounts run pretty well - only El Captain Users have this issue so far.

Please excuse my bad english - it is not my native one.

Help or any ideas on this are appreciated.

Thanks, Norman

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Bruce Barnes Replied

11/4/2015 at 7:48 AM

Notification of this was given at the very top of the Version Notes when the release was made public on Monday evening

Version: 14.4.5784 (November 2, 2015)

UID validity values of 0 are no longer used when syncing with IMAP as required by the IMAP RFC. This will cause all folders synced with IMAP that had a UID validity value of 0 to re-sync all messages, resulting in a large spike in bandwidth usage for a short time after installation.

Bruce Barnes ChicagoNetTech Inc brucecnt@comcast.net Phonr: (773) 491-9019 Phone: (224) 444-0169 E-Mail and DNS Security Specialist Network Security Specialist Customer Service Portal: https://portal.chicagonettech.com Website: https://www.ChicagoNetTech.com Security Blog: http://networkbastion.blogspot.com/ Web and E-Mail Hosting, E-Mail Security and Consulting

Norman Roy Replied

11/4/2015 at 8:18 AM

Hello Bruce,

thanks for the reply - of course i´ve read the note. The problem is not resyncing the IMAP Folder, the problem is that it is permanently reloading.

A sample mailadress has 1Gigabyte data - so it should produce max 1 Gig of resync. But it actually produces 250 Gig a day because it is stuck in a permanet reload, ignoring the actual size of the IMAP Stucture.

Bruce Barnes Replied

11/4/2015 at 8:43 AM

Have you done a search of the IMAP logs, under the user's e-mail address? (make certain they are set to detailed.)

If so, what do those logs tell you?

You can also try to delete the user's account from the DEVICE to see if the resync churning stops. If not, they may have additional devices running IMAP on the account - not at all uncommon.

If deleting the user's account from the device stops the churning, they try rebuilding the account on the device, and see if that helps.

Failing that, open a ticket with SmarterMail.

Norman Roy Replied

11/5/2015 at 1:17 AM

Hello Bruce,

thanks for your Feedback, it seems that the problem could be solved with the delete of the user accounts. The customers weren´t very pleased but glad it solved the problem.

Interesting: The problem occured not on all mail accounts of the domains, only some. We checked the client configuration and the settings were exactly the same. So it can´t be a server problem.

Thank you for your help Bruce!
Cheers
Norman

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