Email errors when sending. Cannot send.

When trying to send mail via eM Client desktop (my desktop mail app), I am getting the error, “Authentication failed with reason: Unexpected End of Stream”. I have not changed any email settings; I have checked my settings and find everything to be okay. When I log directly into my ISP account via web, I can both send and receive. The send mail does not work in eM Client desktop. I also get an error , “5.1.0 sender rejected - POL108” I have checked with my ISP and they say everything is good on their side. My account is active and working fine. Any help here? Thanks!

Hi, what version of eM Client are you currently using? What mail service are you using? Can you please make a screenshot of the error(s) and post it here on the forum?
Also when the error occurs, can you please switch to the Log/History tab and copy the content of the log as well?

Thank you,

The problem disappeared after a few hours.  Juraj Micek responded back from a support ticket at eM Client.  He said it was a firewall issue.  If it appears again, I’ll follow up as directed below.  
Thank you so much for responding!

No problem, glad it works, keep us posted if you come across this or any similar issues, we’ll be happy to help.