Error message Sender Domain Invalid (VM424)

[acidfast]

Can anyone help with a problem that developed overnight?

I have my own domain and use my virgin eMail account to send and receive messages.  The eMails are set up to point at virgin media and the SPF and DMARC are correct and were working correctly yesterday.

This morning I cannot send eMails but receive them fine.

The error message I get each time I try to send is

550 5.7.0 Sender Domain Invalid (VM424) yB9KlzFaEUrTayB9KlvMiY

Any help gratefully received.

[acidfast]

Hi Rob,

Can we know what was fixed so that we know what to say to the helpline next time this happens as they did not seem to have a clue this time and looking at the archives it appears to be a regular issue?

Thanks

[ravenstar68]

@acidfast 

Good luck with that one 🤔 VM often play their cards very close to their chest.  Even if they did tell you, unless phone support gets a considerable uplift, it's doubtful that they'd understand, much less know who to pass the matter on to.

From my perspective, given the error code and the fact that it was happening after the DATA send, it looks to be some sort of failure related to the DMARC module (DMARC works based on the From: header, something the server only sees after the message has been sent.  (Think of From: as being the address on a letter rather than the address on the envelope).

Failing that I couldn't say exactly what was going on.  I do know that it was causing problems for people using different authoritative DNS servers.

Tim

[ravenstar68]

It looks like VM have been updating their mail setup and initially hadn't amended the DNS lookup for _smtprelay.virginmedia.com

Tim