Mail errors · Gmail

What does “451 4.7.24 The SPF record of the sending domain has one or more suspicious entries” mean?

Gmail found entries in your SPF record that it treats as suspicious.

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

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451 4.7.24

The SPF record of the sending domain has one or more suspicious entries

As Gmail prints it.
01

What does it mean?

The record lists who may send as your domain. When it lists far more than the services you use, it no longer tells a mail server anything.

02

What exactly does the source say?

451 4.7.24 The SPF record of the sending domain has one or more suspicious entries. To protect our users from spam, email sent from your IP address has been temporarily rate limited. For more information, go to Email sender guidelines.

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

Same fix: 550 5.7.24
550 5.7.24 The SPF record of the sending domain has one or more suspicious entries. For more information, go to Email sender guidelines.
03

Why would a small firm see it?

An old entry nobody removed, a very wide range of addresses, or a record that ends in +all, which the standard reads as pass for every server.

04

How do I fix it?

  1. Read your SPF record: the TXT record at your domain that starts v=spf1.
  2. Match each entry to a service you use today.Take out the ones you cannot match.
  3. End the record with ~all or -all, never +all.

Keep one SPF record. Add the service inside the one record you have, before its last word, and keep every service already in it. A second SPF record makes the check fail for every message.

An SPF record may make at most 10 DNS lookups. Each include counts, and so do the includes inside it. Past 10 the check fails, so take out services you no longer use before adding a new one.

05

What else do the sources say?

The "all" mechanism is a test that always matches.

possible qualifiers, and the results they cause check_host() to return, are as follows: "+" pass "-" fail "~" softfail "?" neutral

Sources

Where does this come from?

Related
07 · Check my firm

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