Can't load Gmail messages: UNIQUE constraint failed: MailCategoryNames.categoryName,

I upgraded eM client, and now it crashed immediately on loading with this error:

eM Client (7.0.27943.0)Windows: Microsoft Windows NT 10.0.14393.0, Framework: 4.0.30319.42000
The following error has occurred:
System.Data.SQLite.SQLiteException (0x80004005): constraint failed
UNIQUE constraint failed: MailCategoryNames.categoryName,
   at System.Data.SQLite.SQLite3.Reset(SQLiteStatement stmt)
   at System.Data.SQLite.SQLite3.Step(SQLiteStatement stmt)
   at System.Data.SQLite.SQLiteDataReader.NextResult()
   at System.Data.SQLite.SQLiteDataReader…ctor(SQLiteCommand cmd, CommandBehavior behave)
   at System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.SQLite.SQLiteCommand.ExecuteScalar()
   at MailClient.Storage.Data.DbItemRepository1.StoreCategoryName(UInt64 parentId, String categoryName) &nbsp; &nbsp;at MailClient.Storage.Mail.Data.DbMailRepository.\<\>c\_\_DisplayClass95\_0.<store>b__0(String i)<br> at MailClient.Storage.Data.CategoryNameCollection.From(IEnumerable1 values, Func2 storeValue)<br> at MailClient.Storage.Mail.Data.DbMailRepository.Store(IMailRepositoryItem mail)<br> at MailClient.Storage.Data.DbRepository1.Add[ST](Object senderContext, IEnumerable1 items)<br> at MailClient.RepositoryExtensions.Add[T,ST](IRepository1 repository, IEnumerable`1 items)
at MailClient.Protocols.Imap.Synchronizer.SynchronizeMessagesCommand.Fetch(FetchNotification response)
at MailClient.Protocols.Imap.Synchronizer.Fetch(Folder folder, FetchNotification response)
at MailClient.Protocols.Imap.Synchronizer.ImapNotification(ConnectionPoolEntry connectionPoolEntry, Folder activeFolder, NotificationEventArgs e)
at MailClient.Protocols.Imap.ConnectionPoolEntry.Connection_Notification(Object sender, NotificationEventArgs e)
at MailClient.Imap.Base.Connection.ParseUntagged(String line)
at MailClient.Imap.Base.Connection.ParseReply(String line)
at MailClient.Imap.Base.Connection.ReceiveWorker()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

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eM Client

Hello Ryan,

We’re sorry for the inconvenience. This unfortunately means that your database has been damaged.

You will need to start with a new database (please note that your local data and program settings will be deleted). If eM Client can’t find the database folder in the default location with the default name, it will create a new one. To start with a new database, simply turn eM Client off and rename the ‘eM Client’ folder in C:\Users\username\AppData\Roaming to e.g. ‘eM Client old database’.

If you have a backup from version 6, you can unzip the backup file and Import the data through Menu -> File -> ‘Import…’ - ‘Import from version 6’


Maurice, How do I go back to version 6 EmClient!  This is unacceptable.  I have a backup but 7 doesn’t recognize it.  I lost ALL my contacts! I would like to restore emclient 6.  How?

Hello Vera,
just uninstall eM Client 7 and install eM Client 6 again. The installation file is on our download site under the main button and in the release history.
You can then restore from your backup.

eM Client 7 should recognize backup files even from eM Client 6 though. What error message pops up?
As for your contacts - which ones are missing? What account are they connected to?