Postfix email address recipient

Hi All,
I’m new to postfix. I planning to setup a mail server on ubuntu server 20.04 LTS.
I follow this guide:

Everything is working well, I managed to send and receive mail.
But one thing strange is when I send mail to my gmail account, it show the recipient email address with [email protected] instead of [email protected].
Why will this happen? What configuration am I missed and what should I check?

The From: domain name is determined by the myorigin parameter in Postfix.

[email protected]:~$ postconf myorigin
myorigin = /etc/mailname
[email protected]:~$ cat /etc/mailname

Thanks for your reply, but the method I tried still same.
Default in /etc/postfix/
myorigin = /etc/mailname (the result is same)
I tried:
myorigin = mydomain,com (the result still same)

My /etc/mailname already is mydomain,com.

But there is weird if I use echo “testmail” | sendmail [email protected],com
The result From: is correct which is [email protected],com.

(Sorry i use comma instead of dot because of restriction of new users)

This means your Postfix configuration is correct.

But the address still display as

You said earlier that “The result From: is correct which is [email protected]”.

By default, Postfix allows you to use any domain name in the From: address. If you don’t specify a From: address in your email, then Postfix will use

The From: address will be displayed as when you explicitly set it as the From: address.

I means if I use → echo “testmail” | sendmail [email protected],com this command, the result is

But if I use → mail [email protected],com this command, the result is

so it correct or wrong?

This is correct.

By default, the mail command uses the OS hostname in the FROM: address. You can set the From: address like below.

mail -a FROM:[email protected] [email protected]

or you can change the OS hostname to mydomain .com.

sudo hostnamectl set-hostname mydomain .com

In Postfix file, you should set

myhostname = mail.mydomain .com