SMTP enhanced status code 4.7.12

What the registry says

The basic codes it travels with

• 432 A password transition is needed

In practice

As an authentication code, X.7.12 asks the user to log in once with PLAIN to move to a new mechanism, and it is rarely seen. Microsoft 365 reuses 550 5.7.12 for a recipient set to reject mail from outside its organisation, which is the meaning most people search for. Only the recipient's administrator can change that.

What the sender should do

For authentication, log in once as the server describes. For the Microsoft recipient restriction, only the recipient's administrator can allow outside senders.

How providers use X.7.12

Quoted from each provider’s own error reference.

• Microsoft 365 5.7.12

  Sender was not authenticated by organization

Common questions

What does 4.7.12 mean?

X.7.12 means the user must make a one-time transition to the selected authentication mechanism, typically by logging in once with PLAIN. Microsoft also uses 5.7.12 for recipients that reject mail from outside their organisation.

What should I do about 4.7.12?

For authentication, log in once as the server describes. For the Microsoft recipient restriction, only the recipient's administrator can allow outside senders.

Would an email verifier have caught 4.7.12?

No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.

Full guides for this code

• 550 5.7.12 — Sender not authenticated by organization (Microsoft 365)