Mail errors · Gmail

What does “550 5.7.1 Messages missing a valid address in the From: header, or having no From: header, are not accepted” mean?

The message had no From line, or a From line without a valid address.

Last read from the sources at the foot of this page.

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Gmail bounce
Mail Delivery Subsystem
550 5.7.1

Messages missing a valid address in the From: header, or having no From: header, are not accepted

As Gmail prints it.
01

What does it mean?

DMARC is checked against the domain in the From address. A message without one cannot be checked, so Gmail refuses it.

02

What exactly does the source say?

550 5.7.1 Messages missing a valid address in the From: header, or having no From: header, are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.

Gmail's page writes domain-name and ip-address where your bounce shows your own domain and the sending address.

03

Why would a small firm see it?

A website form, a script or a device whose From setting is empty or carries only a name.

04

How do I fix it?

  1. Find what sent the message.
  2. Set its From address to one real address at your own domain.
  3. Make sure the service that sends it passes SPF or DKIM for that domain.
05

What else do the sources say?

Format messages according to the Internet Message Format standard, RFC 5322.

Sources

Where does this come from?

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