Hey there,
Are you still having issues with this?
I haven’t come across this myself, I’m afraid, but I’ve had a search around for that Error Message
I’ve come across a few suggestions, that might be worth giving a try?
-
Have you tried enabling Less Secure Apps for your Google account?
https://www.google.com/settings/security/lesssecureapps -
There is also this post here, in which the user notes that changing his password resolved the issue:
Gmail "Too many login failures" in SugarCRM | How 2 Guru -
There is also this post, detaiing that the Gmail Domain may need a DKIM:
g suite - Google SMTP Error: 454 4.7.0 Too many login attempts, please try again later - Server Fault
Unfortunately, as I can’t replicate, I’m not really able to investigate these solutions 
However, do any of the above sound like a step in the right direction?