error in client/server conversion

I have set up my mail at in eM Client. It seems to be working for the most part, I can download my emails, read them, see all folders and even send email.
What does not work is marking emails as read. They are then marked in eM Client, but I get the following error:

“Error in client/server conversion”

This appears once for each and every email that I mark as read, or for that matter, mark as un-read. It is not marked as “read” when going to the website.

A few additional details that might have an impact on this:

  1. I’m using a custom domain name, so it’s not “” or “
  2. I had to change the server from “” to “”. Using the hotmail server, I could only sync folders, but got a connection error when trying to sync email.

Here’s the full log I get - stars in domain name due to privacy, but there’s no strange letters or anything used:
00:39:01 Online state: changed to online due to NetworkAvailability 00:39:01 simon@ta**** [AirSync]  Synchronizing folder list
00:39:05 simon@ta**** [AirSync]  Synchronizing folder list
00:39:08 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:41:13 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta**** Bundle/’
00:41:44 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:52:34 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta**** Email/’
00:52:41 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:53:22 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:53:30 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:53:38 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:53:46 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:54:34 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:55:05 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:55:13 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:55:20 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:55:29 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:55:34 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:55:42 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:56:00 simon@ta**** [AirSync]  Uploading item(s) to folder ‘simon@ta****’
00:56:02   MailExceptions.OperationException: Error in client/server conversion.
00:56:02 simon@ta**** [AirSync]  Uploading item(s) to folder ‘simon@ta****’
00:56:05   MailExceptions.OperationException: Error in client/server conversion.
00:56:05 simon@ta**** [AirSync]  Uploading item(s) to folder ‘simon@ta****’
00:56:08   MailExceptions.OperationException: Error in client/server conversion.
00:56:08 simon@ta**** [AirSync]  Synchronizing folder list
00:56:11 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta****’
00:56:21 simon@ta**** [AirSync]  Synchronizing folder ‘simon@ta**** Bundle/’

Anyone know how to solve this? This happens on two PC’s where i’ve tried eM Client. Syncing works just fine on other devices I have, that are not using eM Client, such as my android phone.

Hi Azthal,
have you tried setting your account up as IMAP instead of AirSync?
You can do it by manually setting up your account in Tools>Accounts>New account and instead of the automatic setup choose Mail>Other and configure your incoming and outgoing servers.


Hi Olivia,

Thank you for your answer.

Yes, IMAP does work, but unfortunately does not cover my needs. I specifically want to use AirSync/Exchange (not quite sure of the differences) because that also lets me sync my contacts and calendar. That is the whole reason I decided to use eM Client in the first place.

Anyone know of a solution to this? I have read other posts where it’s claimed that this is due to server issues. That is not really a satisfactory answer though.

eM Client claim to have full support for This does not appear to be the case, you only have standard IMAP and POP support.
Blaming it on the “servers of” doesn’t really make sense, considering it works just fine from other devices and software. I’m assuming that comes down to the type of connection you are using (AirSync vs ActiveSync, whatever the difference may be).

Now, I would be alright with using IMAP for email, if I could still sync my calendar and contacts in some other way, but that does not seem to be the case?

Is there any solution for this at all?

Hi Azhal,
I’m sorry for the late answer and for the inconvenience. AirSync and ActiveSync are the same thing. The problem might be with Microsoft’s plans to disable the Air/Active sync alltogether and we are trying to accommodate to this change and find a way to sync Contacts and Calendars over a different protocol. We are working on a solution.