Google WorkSpace – SMTP Relay Failure – SMTP protocol error. 550-5.7.1 Daily SMTP relay limit exceeded for customer

SMTP Relay Errors

Google WorkSpace have insisted on migration of all customers to new subscriptions.

Whilst on the surface, it looks like it’s just an update to the existing subscription. New name etc, it’s actually a cancellation of the old subscription and a new subscription in Google’s backend.

To the user / admin it shouldn’t make a difference. And for day to day, general use, it doesn’t.

However, if you use the for sending out emails from a scanner or an app that can’t do 2FA etc, then you might be badly impacted. Even if you’re authenticating by IP etc.


An existing customer, paying their longstanding WorkSpace subscription, gets a certain level of trust inside Google’s SMTP ecosystem.

The daily limits for the amount of relayed SMTP are pretty high and you’re unlikely to bump into those limits.

The daily customer limit for a trusted Google WorkSpace customer is millions of relayed emails apparently.

A new customer, one on a trial subscription or that appears as “new” to Google, well.. that’s not the case. The limits are lower. Much lower. In fact they’re so low, that it’s quite easy (a few dozen per day) to bump into them. And as an admin you can’t do anything about it.


What is the root cause of bumping into the limit?

The giveaway is that you’ll be getting lots and lots of

SMTP protocol error. 550-5.7.1 Daily SMTP relay limit exceeded for customer

in your logs.


That change in subscription?… ..yeah… you are now a “new” and “untrusted” customer. Your limits are reset accordingly.

Google support contradict themselves about this SMTP relay limit – but eventually (many days later) you’ll get that as the root cause.

What can you do about it?

  • You can’t not change subscriptions, Google are forcing the change, whether you like it or not. So not an option…
  • You could raise a support ticket to get them to amend your limit before you migrate. But probably not..
  • You could wait many days with email being rejected and a P2 case open before they fix it. Not ideal really..
  • Stop using the relay service and start using and proper authentication. But you’d already be doing this if your app / scanner / whatever could do it.. right?
  • Or, you could have another SMTP service ready to go (eg. AWS SES) for if / when the Google Relay starts rejecting you.

Very irritating..

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