SMTP enhanced status code 5.7.30

What the registry says

The basic codes it travels with

• 550 Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons)

In practice

X.7.30 belongs to REQUIRETLS, from RFC 8689, which lets a sender insist on TLS for every hop. Very few senders use it. Gmail uses 421 4.7.30 and 550 5.7.30 for bulk mail that failed DKIM, which is the meaning most people see.

What the sender should do

Send without REQUIRETLS or through a path that supports it. For Gmail's use, set up DKIM.

How providers use X.7.30

Quoted from each provider’s own error reference.

• Gmail 421 4.7.30

  Your email has been rate limited because DKIM authentication didn't pass for this message. Gmail requires all email bulk senders to authenticate their email with DKIM. Authentication results: DKIM = Did not pass. To set up DKIM for your sending domains, visit Set up DKIM. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

• Gmail 550 5.7.30

  This message was blocked because it didn't pass DKIM authentication. Gmail requires bulk email senders to authenticate their email with DKIM. Authentication results: DKIM = did not pass To set up DKIM for your sending domains, visit Set up DKIM. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.

Common questions

What does 5.7.30 mean?

X.7.30 means the message required REQUIRETLS under RFC 8689, and no server on the next hop supports it. Gmail also uses 5.7.30 for bulk mail that failed DKIM.

What should I do about 5.7.30?

Send without REQUIRETLS or through a path that supports it. For Gmail's use, set up DKIM.

Would an email verifier have caught 5.7.30?

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.