Office 365 Exchange syncing very slow/hanging

Really hoping there is some way of resolving this issue, as it’s probably the only deal breaker for moving away from Outlook and over to eM Client.

I have an Office 365 account and have successfully connected to that mailbox using Exchange Web Services syncing.  The issue is that the syncing is either incredibly slow and on some occasions it hangs the whole eM Client application, forcing a Task Manager app close.  This then forces a database rebuild on reboot of eM Client.

I also have an account and the ‘Air Sync’ has similar but not as bad issues.  It’s sometimes slow, but hasn’t yet frozen the whole app.

I also have 10 IMAP accounts and all IMAP folder subscriptions work perfectly, so this is not a general syncing issue.  One of the IMAP accounts has 25,000 messages in the inbox with no issue at all!

Is there a setting I’ve missed (I’ve already changed the sync interval to 60 minutes to reduce the effect of this issue)?

Hi Nico, if I understand this correctly your application freezes only when you have the Exchange Web Services account setup (enabled) in eM Client?
Have you submitted stack dump from this issue to any of our support staff possibly my colleague Wilson or Micek?

If not, could you please download this utility and run it while the application is frozen and submit the file to my email [email protected] with a reference link to this forum topic?

Thank you,

Hi Paul, I’ve not communicated with any support staff previously about this.

Unfortunately, eM Client is hanging yet again and is now unusable for me.  I really hope you can fix it, but for now I’m going to have to stop and go back to outlook.

I’ll send you the stack dump now.

Thanks for your help.

Hi again Nico, can you please comment on what are the issues currently then? Is it an issue with the Exchange account only or other accounts as well?
What account are you seem to be having issues in the stack dump you’ve sent me?

Thank you,

Hi Paul,

As I said, I have 12 mail accounts set up, 10 IMAP, one and one Office 365.

The rotating circle next to each folder heading shows which account/s are being updated/synced.  All of them sync quickly and correctly (and the rotating circle thus disappears), except the Office 365 Exchange account. This just updates continuously.

Sometimes mail is still accessible whilst the syncing is taking place, other times (including when I ran the stack dump I sent you) the syncing stops mail from being visible and clickable, meaning I cannot read or send any mail from that account. On other occasions, the whole eM Client hangs and has to be closed with task Manager.

So, to summarise: the stack dump I sent you should show mail attempting to be synced with a hosted Exchange 365 account, but just hanging.

I’ve never had an issue syncing this account using Outlook 2013 and still don’t even when eM Client is hanging.

Hope this helps.

Hi Nico, I’ve discussed the issue with the developers and it seems like there might be an issue with a rule (possibly blacklist).
Do you think you could submit your settings.xml file from your database folder to us? This would help us determine where the issue might be caused for quickly finding a solution.

Thank you,

Hi Paul - many thanks for your help - will do.

Meanwhile, I’m going to disable the only rule I have set and see if that makes a difference.

Hi again, great, thank you.
I forgot to post details on where to submit the settings file, please send it to [email protected] with a reference link to this forum topic, just as you submitted the stack dump.

Thank you,

Hi Paul, the slowness/hanging did seem to be related to a rule I had set.  Deleting the rule seemed to fix the problem.  Not an ideal solution, but liveable for now. The rule included looking for several words ‘found in the subject or body’. This causes the rule to run very slowly, although it ran OK on an IMAP mailbox with 25,000 messages, whereas the Exchange mailbox only has around 2,000.

I received notification of an update to a new version this morning and have now upgraded and also set up a new, simpler rule.  This all seems to be working…fingers crossed!

Hi again Nico, that is very interesting, do you have “Download messages for offline use” option enabled on your account?
Since eM Client only downloads the headers of messages without this option enabled this might be causing issues when the body is not actually downloaded before the rule is processed.

Thank you,

Hi Paul, no, I have not enabled “Download messages for offline use” on any IMAP account.

I assume the ‘Subject’ field is a text field with a maximum number of available characters? Creating rules that look for words in the ‘Subject’ field works very fast.

Looking for words in the ‘Body’ runs much slower; is the data type for ‘Body’ a memo type field?  Perhaps this explains the big difference in performence?  Or am I completely off on a tangent here?

Both are practically unlimited in size. And in both cases the performance is
relative to the actual data size. In addition the body is not downloaded by
default on IMAP and it has to be explicitly downloaded if some rule depends on

Hope this helps,