To get the header of an email in Gmail

the first thing we have to do is go to our email (in the Gmail inbox)

as we see this email is still unread

we enter the email:

and in the 3 circles on the upper right side, different options appear

we click on show original:

and a new window will open with the original email:

This code is the original message and headers

therefore, when the headers of an email are requested, we can see them from Gmail in this way