hi there !
how SSH into my Ubuntu server to Build or Send an Email?
is it true to use iRedMail?
Welcome to the forum.
That's quite a question that you're asking. The answer would be very long and you're not stating your Unix/Linux skills.
I suggest that you start here and then feel free to ask us all somewhat smaller more specific or error message questions.
iRedMail is one option.
I hope that helps.