I can't synchronize my Exchange account on Mail app.

Exact same problem, started exact same time... tried to rebuild and this caused the inbox to disappear and not rebuild. Curiously, yes, not only can I see the other folders (like sent folder) from my Exchange accounts, I can still send email. I have the same "invite" related constant stream of error messages. Does anyone have a sense if whether a particular calendar invite should be deleted from the inbox (via web client or one of my other devices (iPhone and iPad working just fine)) might help the problem? p.s., also tried restoring the inbox from Time Machine and that does not work. Thanks!

I've also been seeing this issue on an iMac running OS X 10.11.6. First occurred for me on July 24th when I received a calendar invite for a group meeting. One of my coworkers who is also on 10.11.6 started seeing this issue after receiving a calendar invite on August 1st.

I can confirm Mail.app will work if you find and delete the calendar invite email (from Inbox first and from Trash second) through some other client. Calendar.app does not work at all for my exchange account though.

Also, I found that if I send a calendar invite from Calendar.app (from a different Mac running macOS Sierra), I end up with 5 to 10 emails in Sent/Trash that I have to delete before Mail.app will work again.

Same problem here. Everything fine until the 27th. Tried doing everything I could think of to fix the problem. Same thing that were mentioned before. Its not affecting my iPhone or iPad, but my macbook and iMac are no longer receiving emails and the inbox is empty.

Yup. This started for several that I know, including me, somewhere between Jul 29 and Jul 31 (aka over the weekend while not at the office – perfect time to roll out "improvements"). Exact same symptoms and log messages. Partial solution is to try to delete meeting invites using another client, but that has not been completely successful (they've been coming back), and it's a lame solution. Our ITS (unnamed very large university) is clueless, as usual lol – this thread is the only corroboration I've found, and the 18 hour window (3 days now - cough cough) is obviously a lie on someone's part (too many targets to choose from). The upgrade to Sierra is a known solution, and of course ITS prefers the easy way out (just use the Very Fine - not - web client, what's your problem). For those of us who prefer Mail, or, more importantly, need El Cap for specific hardware reasons, we're screwed. Good luck, suckers!

PS this is absolutely not related to the Security Update. Proof: reinstall El Cap, which immediately asks you to do said security update (003, dated 19-Jul). The problem remains without applying the update. This also suggests that the issue has nothing to do with Mail or any pref corruption etc, as I started from a clean slate (plist, etc) as a result of the reinstall. A Time Machine restore from before when the issue began also did not work. This is almost certainly O365, as has been alluded to in this thread.

Agree 100% with jeglin, everything points to something changing on the Office365 server end, and no changes on the Mac end. Even 10.6.8 mail started having this problem at the same time. They must have changed something in the communication protocol that was never encountered before by all of the Mail.app implementations before Sierra, and wasn't handled the way MSFT would have expected. Security updates and preferences have nothing to do with this issue.

Also, deleting the recent problem email / meeting message will likely have mixed results. For users that have been regularly syncing with the server, it may work because of only downloading the new messages, but if you're setting up a fresh Mail.app configuration and need to download ALL inbox messages from the server, it will likely fail if ANY have that issue.

And Microsoft documents that Office365 mail will work with Mail.app going as far back as Snowleopard. It would be great if the live up to that and fix this issue.

Access your account using a Mac - Outlook

For me, I have a high priority user (my wife) that really can't wait any longer, so Sierra is going to be the solution for her so I will likely not be monitoring this problem once she has been converted.

From MS:

Estimated time to resolve: We expect this issue to be completely resolved for all affected users within the next 3-4 days as the fix is safely implemented through our change management process.

Meanwhile, back at the large university...

Over the weekend, I was able to partly fix this by running a search+destroy mission through about 30,000 messages (using Outlook) for ANY calendar invites. When I had finished committing these murders, with some victims going back to 2013, many of my e-mails then started to appear in the Apple Mail client. But not all.

At this point now, a couple of days later, I concur that it does appear that service may have been restored, after a week; however, I'm still comparing my Mail folders to my Outlook folders to prove this to myself.

My apologies to Exchange Administrator EHLO-Ben at our large university for my unprofessional insults on a public forum. I've already sent an apology to the other ITS person involved.

Contacts app still has issues, though:

FYI it seems like the invite that "killed" things for me was from join.me this morning July 31st, not sure if others saw invites from join.me being the issue, or if from other sources?

Hi Alan,

did you get to the bottom of this at all? We are getting the same errors in the logs...

Cheers,

James

Sierra fixes it! Thanks chrisblt for the note, you saved me lots of back-and-forth troubleshooting with Microsoft support. I upgraded to Sierra and the problem is gone.

On a computer that I can not upgrade to Sierra. Office365 has been working fine for a long time on El Capitan. Apple or Microsoft needs to fix this.

I just opened a ticket with Apple last night. It appears that Security Update 2017-003 may be the issue. I'll post updates after I hear back from Apple.