I've worked with web servers but never with a mail server. I would like to know how it works with the internet infrastructure. I have some ideas and questions and would like to get the "big" picture.
the mail server can use the same IP as the web server right? only it uses different ports. POP3 and IMAP inboxes are mail server user accounts right? using a mail server to send emails (via applications) only doesn't require any user accounts other than admin and system accounts right?
How are email addresses "email@example.com" mapped to the mail server accounts? I've got domain and web hosting from providers recently setup to work together, and I figure the domain registrar DNS forwards your domain emails to the mail server. the mail server looks at the first part or "username" of the email address of the email received and determines which user's inbox on the server to send to. if none, send to some default inbox. so then do you specify a domain name for the mail server configuration also to append a domain name to the user account for outgoing mail sent via the user accounts? and if domains are mappings for IP addresses then, are such emails as firstname.lastname@example.org usable? (although awkward)
so does this mean the DNS server sends domain emails to the mail server and mail server routes emails accordingly to user accounts and thus doesn't deal with domain stuff in the email addresses other than what was set in the server configuration for mail server domain to use?
Does that mean mail servers don't really work without a DNS server for POP3 and IMAP but is ok if using SMTP only? Or can you send email to server by means of user@server_IP for POP3 and IMAP?
I want a complete, concise reply on this that answers all questions. thanx for your help.