Mail errors · Gmail

What does “550 5.7.1 Messages missing a valid Message-ID: header are not accepted” mean?

The message had no valid Message-ID line, which every message is meant to carry.

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 Message-ID: header are not accepted

As Gmail prints it.
01

What does it mean?

A Message-ID is a unique label for each message, part of the standard format for email, RFC 5322. Gmail refuses messages without one.

02

What exactly does the source say?

550 5.7.1 Messages missing a valid Message-ID: 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 that builds its own messages.

04

How do I fix it?

  1. Find what sent the message: a website form, a script or a device.
  2. Send through your mail provider, or set the software to add a Message-ID.
  3. Send a test message to a Gmail address and check it arrives.
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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