Just wondering if anyone using a Gmail account to send alerts from ACP has had any issues recently?

I had one failure today from ACP

2018-05-29 06:59:55.7: Observatory startup succeeded in unsafe weather.
2018-05-29 06:59:57.4: Email failed: Failure sending mail.
Smtp server returned an invalid response.

I've also had Gmail stop sending emails from a custom piece of roof control software in the last week.

I know they did a big upgrade of the front end of their software. I am wondering if they've changed the backend as well and if this is causing issues with third party programs that send email from their accounts???

Thanks in advance for any comments.

ta
DT