What the message looks like
550 5.7.27 Sender address rejected: Domain example.com does not accept mail (nullMX)Domain example.com does not accept mail (nullMX)
What it means
The domain has published a "null MX" record, which is the domain owner's way of saying it never receives email. Domains used only for a website often do this.
You'll see it in two situations:
- The sender's domain has a null MX. The standard name for this is "sender address has null MX", status
5.7.27. Receiving servers reject the email, because nobody could ever reply to it or receive a bounce. - Gmail, for bulk senders. Gmail also uses
5.7.27when a bulk sender fails SPF, which is a different problem. See 550 5.7.26. - The recipient's domain has a null MX. The sending server doesn't even try to deliver, and reports that the domain doesn't accept mail, often with status
5.1.0or5.1.10.
If you're the recipient
If emails to your address bounce with this, your domain is set up to refuse mail. If you want to receive email, replace the null MX record with MX records from your email provider.
If you're the sender
If your own emails are rejected with 5.7.27, your sending domain has a null MX record. Either send from a domain that receives email, or replace the null MX record with real MX records. Apps and websites often send from a domain like noreply.example.com that has one.
If you use addy.io
addy.io rejects emails from senders whose domain has a null MX, with 550 5.7.27 Sender address rejected: Domain example.com does not accept mail (nullMX). You can't fix this from your account. The sender has to send from a domain that accepts email.
If the error is about your recipient's domain, that domain can't receive the emails addy.io forwards. Add a different recipient that can.