Received an email from [email protected] What would that mean?

Question

Email

I experimented with installing Mattermost on various BSD systems (virtual machines), and it seems that at some point I specified my real email address as email. And I found an email from [email protected] in spam. As you know, example.com is generally a test domain for examples in the documentation, although it really exists. And the letter seems to have been sent by my freshly installed Mattermost. But I definitely didn’t set up the mail transport on Mattermost (this is not necessary in test installations), the question is - how could he send me a letter, and even from such a box?

Answer 1

means you are new
PS see email headers

Answer 2

Let me send you a letter from [email protected] And you will receive it. And not necessarily spam.
PS. Look at the letter headers, learn how smtp works in general. It was simply designed for fair use.

Answer 3

From text box
At one time when doing mail about spam and imbeciles they didn't think about it, everyone thought that from would always write themselves.
Up to the fact that SMTP had no authorization at all.
Where is it before checking the sender's name.