On certain overviews you will sometimes see the invalid email icon .
This can have different causes, to help you find the issue we made a check-list:
If you have a high number of invalid emails this is often due when using your own SMTP server.
The quickest way to verify is to go to Activity - General and look for Email integration errors.
The root cause will often be displayed here.
The email was delivered, but still the invalid email icon is displayed?
In case you use your own SMTP server it is possible that we received a bounce, undeliverable or such from your email server but
that the email is still delivered from your end. In this case verify that your server is sending us the correct delivery response.
Should there have any issues before, the invalid email flag is cleared the next time we could deliver the email for that customer.