Description of problem:
When trying to sync repos, 
Sync Status is "Sync incomplete"
Clicking on the task shows this error:
"getaddrinfo: Name or service not known"

Version-Release number of selected component (if applicable):
Satellite 6.1

How reproducible:
always

Steps to Reproduce:
1. enter faulty SMTP configuration for notifications
2. try to sync the repos
3. fails with error: "getaddrinfo: Name or service not known"

Actual results:
Sync fails when the SMTP configuration for notifications is not set correctly

Expected results:
Sync should still complete even if the SMTP configuration for notifications is not set correctly
The error message should be a little bit more obvious and point to the faulty SMTP configuration

Additional info: