recently I got more and more problems using UploadMessage() of the IMAP module and SendMessage() of the SMTP module of the Mail.dll
I already tried anything mentioned in this blog:
The error occurred infrequently in the past too, but seems to get worse after updating to the recent .NET-Framework version (Windows Update)
Is there any correlation?
What can I do apart from disabling Windows Defender, Antivirus software and increasing the timeouts (ReceiveTimeout & SendTimeout) which I already tested?
When using Wireshark to monitor the data stream, I can see that there are many TCP-Retransmissions. It seems like mail.dll isn't receiving any acknowledgment from the SMTP/IMAP server.
Thank you for your help ;)