Emails won't send

Please help.
I can no longer send emails from anything, Invoice, quotes etc. Please see screen shots attached. I uploaded the newest version of Manager yesterday but still nothing works, I have also contacted my network provider and Apple but without success.
I use a MacBook Pro with Sierra version 10.12.6
Thank you!


It appears you have entered a full email address as your user name. The Username field should normally only contain your account ID.

Tut you’ve been so helpful, all working now.
Many many thanks.