Google has had a major outage over the past two days. Considering 45% of all emails sent by Activity Messenger are to Gmail addresses, this is a problem.
The outage may have affected delivery of emails to your clients that use Gmail in the morning of Dec 14th, and the afternoon of Dec 15th. For example, some of your clients may not have gotten their Zoom link for their virtual class. Fortunately, the problem is now resolved, and new emails are getting delivered.
Gmail outages are very rare but can happen. Here's how you can investigate and overcome such an issue if it were to happen again.
1. Verify the email status
Activity Messenger tracks the status of every outgoing email. A newly sent email has the status Sent. When the email provider receives the message, it sends back an acknowledgement. Activity Messenger changes the status to Delivered.
Now not every email provider acknowledges reception. Yahoo or Hotmail don't always. However Gmail does so reliably. If you see a @gmail.com email address with status Sent, it means there was a problem on Gmail's side. The recipient never got the message.
2. Check your email
If you configured the From email address to your domain, you may have received an error from the Gmail servers saying that an email address does not exist. Something like this:
This is of course not true. That error is a remnant of the outage. You can ignore it.