While it was possible to use Gmail/Google Apps as an SMTP server for scripted use or in any other Apps. I started getting error messages:
SMTP Error: 454 4.7.0 Too many login attempts, please try again later.
Sometimes you get, sometimes you don't get such error.
The issue is because of Google Apps Security. You Can't use same E-mail ID with more than 2 Apps. as Gmail needs to sync it, and it is Obvious to receive such error.
Even setting SPF/TXT/DKIM record is not enough for it.
So try to use different E-Mail IDs for Different Apps.
来源：https://stackoverflow.com/questions/34921053/gmail-app-google-smtp-error-454-4-7-0-too-many-login-attempts-please-try-ag