Email Routing not working since the weekend

I’ve been using e-mail routing for a few months now, but over the weekend it appears to have stopped working. Specifically, emails to [email protected] are no longer routing to the configured destination addresses. Nothing has changed, configuration-wise, since the last email I received.

I’ve also stumbled upon this thread which describes exactly what I am seeing now (although the “turning it off and on again” solution did not work for me).

What is also very strange is that the activity log appears to be empty despite the email summary graph showing activity:

Hi there,

Blake with the Support team here.

Do you see a specific error?

What do you see leading you to believe the routing is not working?

Do you see a specific error?

No errors (although, when trying to disable and re-enable Email Routing and I got some “missing MX record” errors as expected)

What do you see leading you to believe the routing is not working?

Emails stopped being received at the configured destination addresses (personal Gmail account). It worked this weekend.

I am also experiencing this with one of my domains. Routing to gmail doesn’t work, but if I change the route to my old college address (an exchange email), it forwards.
The email bounces with this error:

Remote Server returned ‘521 5.3.0 Upstream error, please check [link blocked] for possible reasons why. Us6Wosh66ecE’

It looks like the rest of my domains are forwarding to the gmail account alright, it’s just one not working as far as I can tell.