It's a surprisingly hard task to educate developers and testers to use the designated test domains (example.com and example.org) in automated or manual tests.

A friend and ex co-worker of mine, at our first job, had to write some code to send emails. Not knowing any better, he ran his manual tests using a clearly non existent email address, just a combination of letters. Or, so he thought: he soon received an email from said combination of letters, begging him to please stop spamming.

I thought the TLD test was meant for this, like mydomain.test.

The relevant RFC lists a couple of options. .test as TLD is valid as well

According to RFC 2606:

> ".example" is recommended for use in documentation or as examples.

Using example.[com|org] for testing feels like shoehorning. I wish IANA had reserved test.com, because that's what feels right when testing.

If you prefer .test then by all means do so. The whole TLD is restricted for that use. Some TLD also have dedicated test domains, any of those is perfectly fine - test.com (or test.de) for that matter is not.

.test TLD is reserved for this kind of testing situations.

Surely example.com has these problems too, although to be fair they don't really need to receive any email.

example.com does not receive e-mail. It is specifically set aside (along with example.{net,org} and a few TLDs) for testing:

https://tools.ietf.org/html/rfc2606

example.com has an empty MX record, so you can't really send email to it anyway.

I believe SMTP attempts delivery to the A record if there is no MX record.

Indeed, if no MX record is known, but an A record is, mail will be sent to that host. However, example.(com,org) are designated testing domains by RFC and any self-respecting mail server should know not to forward mails there. And on top of that, since the domains are designated testing domains, they do not accept mails.

The right thing to do in this situation is to use RFC 7505[1] (Null MX Records).

[1] https://2rfc.net/7505

Cool, didn't know that. Thanks for teaching me something today.

“Empty”? It does not have an MX record.

You're right; I must have misread the dig output. I thought it showed an MX record with no hostname, but that was probably the question section.

Interesting they don't seem to have SPF/DMARC configured properly. That would probably get rid of most spam, at least at major providers.

After setting up a DMARC reporting address for my own domain I was surprised at the amount of emails supposedly from my addresses that are getting rejected, mostly by gmail and yahoo.