**List of steps to reproduce** (step by step, including full links if applicable):
# Register an account on the [[ https://meta.wikimedia.beta.wmflabs.org/wiki/Special:MyLanguage/Main_Page | beta cluster ]] with an email address.
# (Optional) Request a confirmation email.
**What happens?**:
The beta cluster tries to send an email to the mail server (in this case `chlod.net`, where my Wikimedia email lies) of the server requested. The email is denied due to the postfix error "Sender address rejected: Domain not found" because the sender address (`wiki@wikimedia.beta.wmflabs.org`) has a domain (`wikimedia.beta.wmflabs.org`) with no registered MX DNS records.
**What should have happened instead?**:
The email should have been sent properly. At the very least, an MX record for `wikimedia.beta.wmflabs.org` should have been provided in order to prevent mail providers (or local mail servers like mine) from rejecting the email.
**Other information, etc**:
`dig MX +noadditional +noquestion +nocomments +nocmd +nostats wikimedia.beta.wmflabs.org. @8.8.4.4`:
```
beta.wmflabs.org. 120 IN SOA ns1.openstack.eqiad1.wikimediacloud.org. root.wmflabs.org. 1631160002 3600 600 86400 3600
```
`dig MX +noadditional +noquestion +nocomments +nocmd +nostats *.beta.wmflabs.org. @8.8.4.4`:
```
beta.wmflabs.org. 88 IN SOA ns1.openstack.eqiad1.wikimediacloud.org. root.wmflabs.org. 1631160002 3600 600 86400 3600
```
Postfix logs:
```
postfix/smtpd: connect from instance-mx-out03.cloudinfra.wmflabs.org[185.15.56.18]
postfix/smtpd: Anonymous TLS connection established from instance-mx-out03.cloudinfra.wmflabs.org[185.15.56.18]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256
postfix/smtpd: NOQUEUE: reject: RCPT from instance-mx-out03.cloudinfra.wmflabs.org[185.15.56.18]: 450 4.1.8 <wiki@wikimedia.beta.wmflabs.org>: Sender address rejected: Domain not found; from=<wiki@wikimedia.beta.wmflabs.org> to=<wiki@chlod.net> proto=ESMTP helo=<mx-out03.wmcloud.org>
postfix/smtpd: disconnect from instance-mx-out03.cloudinfra.wmflabs.org[185.15.56.18] ehlo=2 starttls=1 mail=1 rcpt=0/1 bdat=0/1 quit=1 commands=5/7
```