Invalid reply format (no Collection)

I am being plagued by this message on my desktop PC, log extract:

09:13:21 [AirSync]  Synchronizing folder ‘’
09:13:22   MailExceptions.OperationException: Invalid reply format (no Collection)
09:13:22    at MailClient.Protocols.AirSync.AirSyncItemSynchronizer2.Synchronize(IItemSynchronizeContext1 synchronizeContext, Folder folder, CancellationToken cancellationToken)
09:13:22    at MailClient.Protocols.Common.ItemSynchronizer`2.<>c__DisplayClass2e.<>c__DisplayClass33.b__2a(WorkerStatus status, CancellationToken cancellationToken)
09:13:22 at MailClient.Protocols.AirSync.AirSyncGenericCommand.Execute(WorkerStatus status)
09:13:22 at MailClient.Commands.Command.Process(WorkerStatus status)

I have replaced my email address with ‘xxx’.

I have 2 eM Client licences and I don’t get this error at all on the laptop so it’s hard to think it’s an problem.

Any suggestions for fixing it?

Hello Jeff,
the problem is with your mail setup - which can be done differently in your devices. This error message is connected to the AIrSync protocol.

AirSync is a mail protocol that has been discontinued by Microsoft. All hotmail and adresses are currently being migrated to Exchange protocol.
You will need to remove your account from eM Client and then either set ip up as Exchange or IMAP (if your particular account hasnt been migrated yet).

If you just installed version 7 the Automatic setup should work for you now. If it doesn’t, you will need to setup the account manually.
To set up your account manually go to Tools>Accounts > New Account and instead of Automatic setup choose Mail>Exchange or Mail>Other.
For IMAP settings your incoming server is and outgoing is


When I set up eM Client on my laptop I exported the settings from the desktop copy and imported then into the laptop. Why should it work fine on the laptop but not the desktop?
I don’t want to set it up as IMAP as my calendar & contacts are on and I them to sunc.

I am trying version 7 to see if it is better. I get the error:

09:09:01   MailClient.Storage.Application.OperationException: Synchronization error (InvalidSynchronizationKey)09:09:01    at MailClient.Protocols.AirSync.AirSyncItemSynchronizer2.Synchronize(IItemSynchronizeContext1 synchronizeContext, Folder folder, CancellationToken cancellationToken)
09:09:01    at MailClient.Protocols.Common.ItemSynchronizer`2.<>c__DisplayClass28_0.b__1(WorkerStatus status, CancellationToken cancellationToken)
09:09:01 at MailClient.Protocols.AirSync.AirSyncGenericCommand.Execute(WorkerStatus status)
09:09:01 at MailClient.Commands.Command.Process(WorkerStatus status)

I am still on MSFT’s old mail system, I haven’t been moved to the Exchange Server yet.

Hello Jeff,
did you migrate your account or did you set it up anew?


I deleted the Gmail and accounts from version 6 then re-booted, installed v7 and added the account. I haven’t bothered with Gmail since they appear to have made a complete mess of people’s contacts moving them from their ‘old contacts’ to their ‘new contacts’ in Gmail contacts.

Hi Jeff,
I see, perhaps your Outlook account has been migrated to Exchange already.
Have you tried to manually set up this account as Exchnage?


There is a useful link here:

According to that I am still on the old system ( NOT Outlook Mail).

Hello Jeff,
thank you for sharing this link as it explains what is going with Microsoft accounts.
Is you account setup differently on your computer compared to your laptop? Can you check the server settings in Tools>Accounts?


They are both using for AirSync.

Is there any news on this please? It also happens on version 7 so I am loathe to upgrade until it is fixed.

Is there any news on this please, it is still happening.

This is still happening, any suggestions? I am currently unable to try version 7 (see separate post) as it complains I have no licence.

Please, please is there any news on this, it is still happening.