Connectivity Error and Suggestion

First off much love to this plugin, been using it for a while now!

So I have a client site who is connected through Google API, and everything *was* working fine… Until it came to our attention emails just stopped going out. So, when I do a connectivity test, it seems that googleapi.com is unreachable on ports 465 and 587… even though those ports test fine for mandrill/mailgun/sendgrid etc.

I noticed some repeat ‘invalid_grant’ errors in the error log, so I renewed the client secret and re-connected… which authorized fine like it did the first time… But, still no luck with the connectivity test on those outgoing ports. No one has installed any kind of firewall to our knowledge and certainly not configured to preventing outgoing ports to the Google API!

For the now I have switched back to sending through the host SMTP, which we had setup before the Google API. Which leads me to my suggestion… if both these credentials are saved, and the Google API email sending fails, could there not be added the option to *FALLBACK* to the server (or other) credentials and sending method?

This way you could have the best of both worlds… Using the primary service you want to, with the extra peace of mind of knowing that if it starts to fail *for any reason* – as it really could be anything – there is a fallback service already in place to pick up the slack without losing emails. I think that would be AWESOME. 😀

Any ideas on the original connectivity problem welcome of course. I’m a bit stumped on what could cause that it really doesn’t make much sense to just stop working like that, although I did read that a change of password can revoke Oauth credentials, and the client did change their password. But still, no connectivity afterwards is strange, especially when the Authorization screen process worked fine.