I am using eM Client with a Mediacom mail account. About 6 days ago, eM Client stopped sending new outgoing messages, they just sit in the outbox. I receive an error message that says “SMTP server didn’t like our greetings and replied with: Unexpected end of stream”. I have tried the diagnose function in eM Client after the SMTP shows as failed, but it cycles through multiple possible host settings, but none work and it says can’t be fixed. I have tried all the recommended smtp server settings for Mediacom I can find on the network, nothing works. Any help is much appreciated!
Unexpected end of stream when sending can sometimes be caused by background resident programs interfering such as eg: optionally installed firewall / security programs or optionally installed antivirus programs or vpns.
So if you have anything like that installed “other than what comes default with your OS”, try completely disabling those to test. Then move the messages stuck in your outbox to your drafts folder and open and try resending them again.