" System.NullReferenceException: Object reference not set to an instance of an object."

This error continually pops up just after syncronizing folders and it usually occurs on the first use of the day.  Here is the error log with all references to my email address removed:

6:48:38 AM Online state: changed to online due to NetworkAvailability 6:48:38 AM  [AirSync]  Synchronizing folder list
6:48:38 AM [IMAP]  Synchronizing subfolders: For folder 
6:48:41 AM  [AirSync]  Synchronizing folder ‘/Calendar/’
6:48:43 AM  [AirSync]  Synchronizing folder ‘/Contacts/’
6:48:46 AM  [AirSync]  Synchronizing folder ‘/Tasks/’
6:48:50 AM  [IMAP]  Synchronizing subfolders: Done
6:48:50 AM  [IMAP]  Synchronizing subfolders: For folder /Inbox
6:48:51 AM  [IMAP]  Synchronizing subfolders: Done
6:48:51 AM  [IMAP]  Synchronizing subfolders: For folder /Sync Issues
6:48:52 AM  [AirSync]  Synchronizing folder ‘/Calendar/’
6:48:52 AM  [IMAP]  Synchronizing subfolders: Done
6:48:52 AM  [IMAP]  Synchronizing messages: For folder /Sent
6:48:54 AM  [AirSync]  Synchronizing folder ‘/Contacts/’
6:48:57 AM  [AirSync]  Synchronizing folder ‘/Tasks/’
6:48:57 AM  [IMAP]  Synchronizing messages: Done
6:48:57 AM  [IMAP]  Synchronizing messages: For folder /Inbox
6:48:58 AM  [IMAP]  Synchronizing messages: Done
6:48:59 AM  [AirSync]  Uploading item(s) to folder ‘/Calendar/’
6:48:59 AM   System.NullReferenceException: Object reference not set to an instance of an object.
6:48:59 AM    at MailClient.Protocols.Common.ScheduleItemUploadContext1.StorageItemToItem(Folder folder, IScheduleRepositoryItem storageItem) 6:48:59 AM    at MailClient.Protocols.Common.ScheduleItemUploadContext1.d__8.MoveNext()
6:48:59 AM at MailClient.Protocols.AirSync.AirSyncCalendarSynchronizer.ConvertApplicationData(EventItem item, Func2 getChildren, Version version)<br>6:48:59 AM at MailClient.Protocols.AirSync.AirSyncItemSynchronizer2.Upload(IItemUploadContext1 uploadContext, Folder folder, IEnumerable1 items, CancellationToken cancellationToken)
6:48:59 AM at MailClient.Protocols.Common.ItemSynchronizer`2.<>c__DisplayClass26_0.b__0(WorkerStatus status, CancellationToken cancellationToken)
6:48:59 AM at MailClient.Protocols.AirSync.AirSyncGenericCommand.Execute(WorkerStatus status)
6:48:59 AM at MailClient.Commands.Command.Process(WorkerStatus status)

So, it this a programming issue? The application continues to work properly after is dismiss the error but it’s continual appearance is frustrating.

Hello Michael,
You might experience problems with your hotmail/outlook/live accounts if you have them setup using AirSync.

AirSync is a mail protocol that has been discontinued by Microsoft. All hotmail, live and outlook.com adresses are being migrated to Exchange protocol.
Since the migration did not happen at once, we changed the default Microsoft setting in eM Client to IMAP for mail combined with AirSync for Contacts and Calendar (because IMAP can’t synchronize those).
It seems your account has been migrated now and the AirSync for Contacts and Calendar no longer works.

You can either just disable AirSync in Tools>Accounts under the General tab of your account to keep the IMAP setup.
Or you can try to setup your account anew by going to New Account and then choose Mail>Exchange.
Use your mail address for both the fields mail account and user name.
The initial setup might take a bit longer.