Email validation is not done for Emails in Server Configuration -> Email log section.
Steps to Reproduce:
Login to Zanata using admin.
Click on admin from left panel.
Click on server configuration.
Go down to the Email log section.
Click on "Enabled" check box.
you will see the Emails field.
Enter any string or number in email field.
Email validation is not implemented for emails field.
There should be an email validation done for emails.
Attached screen captured for more ref.
Fedora 25 + Firefox 50 (64 bit)