Changing from e-mail address in Support System

I have problems with support email and changing the default email of the website to support@domain.com (I don't receive the confirmation link at support@domain.com though if I change to me@hotmail.com or other non domain address it works.

The mass mailer will send email from the support address

I added the line of code as suggested in this thread

https://premium.wpmudev.org/forums/topic/support-system-4

and now I get the error message

Cannot connect to Gmail: Too many login failures

(My domain is set up to use Gmail.)

Does this error suggest I should wait a while before trying again?