Raspberrypi.mail

Internet  |  Raspi 

smtp     ->  [ Postfix ] -> slas-Auth -> System
pop3     ->  [ dovecot ] -> slasl-Auth -> System

postfix

http://www.postfix.org/features.html

apt-get install postfix

main.cf

virtual_maps = hash:/etc/postfix/virtual
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = dovecot

dovecot

https://dovecot.org/

apt-get install dovecot-pop3d