Error "An item with the same key has already been added."

I have attempted to uninstall and reinstall eMail Client to resolve the subject issue, to no avail. The program will not retrieve or send mail.  Here is a copy of the log after uninstall and reinstalling:

6:39:18 AM Online state: changed to online due to NetworkAvailability 
6:39:18 AM Tx.rr (mark.williams9) [POP3]  Connecting: To Tx.rr (mark.williams9)
6:39:18 AM Tx.rr (mark.williams9) [POP3]  Connected: To Tx.rr (mark.williams9)
6:39:19 AM   System.ArgumentException: An item with the same key has already been added.
6:39:19 AM    at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
6:39:19 AM    at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) 6:39:19 AM    at MailClient.Protocols.Pop3.Pop3Account.CheckUids(IEnumerable1 uidsList)
6:39:19 AM    at MailClient.Protocols.Pop3.Pop3ReceiveCommand.Execute(WorkerStatus status)
6:39:19 AM    at MailClient.Commands.Command.Process(WorkerStatus status)

Searching this forum I see that it is an ongoing problem with no apparent resolution. At the moment I will need to uninstall the program and use my old e-mail app.


Uninstalling the application will not make any difference. Rather, try deleting the database and then start again.

To delete the database, close eM Client, and then delete or rename C:\Users_[username]_\AppData\Roaming\eM Client. You may have to show hidden items in Explorer to do that.

You will want to make a backup before you delete the database, just in case you lose anything. You can do that in Menu > File > Backup.

After you delete the database and restart eM Client, setup the POP3 account, then check you have the correct POP3 settings in Menu > Tools > Accounts. The port should be 995 with the security policy set to Use SSL/TLS on special port (legacy).