The default email server for Debian is exim. This can be set up in one of several ways, depending on how you will access your email. The exim configurator will list the options.
Generally, for a networked machine (e.g., Altrop (4.10.20)) that is not acting as a mail server, but using a remote smarthost (SMTP server) to send email, yet still delivering email locally (which is obtained using fetchmail, for example, from an IMAP server), you will choose option 2.
The information you then supply is:
visible name | altrop.ktware.com |
other names | none |
domain rely | none |
network relay | none |
smarthost | mailhost.ktware.com |
root email sent to | kayon |
This means that mailhost.ktware.com is used for sending email. Any email sent from Altrop (4.10.20) to an unqualified address (i.e., no @) will have altrop.ktware.com appended to it and delivered locally.