A Google Mail outage yesterday saw the cloud giant's server respond with the message "the email account that you tried to reach does not exist," potentially causing the sending server to give up, or remove the email address from lists, rather than trying again later.
The outage lasted from around 21:30 UTC until just before midnight UTC according to the company's status report, and it affected a "significant subset of users."
Email outages are annoying and disruptive; but while email has never been a system that guarantees delivery, most do arrive at their destination eventually unless classified (rightly or wrongly) as spam. If there is an error such as a server offline, it will be automatically retried after an interval. Google unfortunately made this less likely, by responding with the message "550-5.1.1 The email account that you tried to reach does not exist." This can cause the sending server to give up immediately, and may also cause the address to be removed from circulation lists.
Email provider ProtonMail informed users attempting to send to Gmail addresses that:
A catastrophic failure at Gmail is causing emails sent to Gmail to permanently fail and bounce back … because Gmail is sending a permanent failure, our mail servers will not automatically retry sending these messages (this is standard practice at all email services for handling permanent failures).
Email (despite its many weaknesses) is used for account verification as well as communications, so this error also caused problems for some third-party services. "Over the past 24 hours, I've had GitHub request that I re-verify my gmail three times (roughly 22 hours ago, 2 hours ago, and now), each time resetting my primary email's status to 'Undeliverable' and 'Unverified'," said a comment on Hacker News.
Another user disputed a transaction on PayPal, assuming that the person with an apparently non-existent Gmail account must be doing something underhand.
"We noticed the issue and mitigated it by transforming the 5xx error into a 4xx error so that messages to Google are re-queues instead of being permfailed. But even with this intervention, the ticket volume was insane,”" said another comment, apparently from the co-founder of email provider MailChannels.
The AWS SES (Simple Email Service) is said to have blocked accounts "because of the high number of bounces."
What can users do if they think that a critical email may have been sent to them but not received? Not much, other than speculatively contacting likely senders to assure them that yes, the account exists, and please resend.
This latest outage follows another more widespread problem two days ago, impacting most Google services and not just Gmail. It is not known whether the two issues are related, but it has been a bad week for Google's users. That said, systems inevitably fail on occasion; but Google should perhaps rethink the circumstances under which its email system reports that a user does not exist. ®