I need a secure email server installed in Debian Lenny with users in a MySQL table.
- The users are from multiple domains.
- Quota should be in MySQL or a global variable for all users.
What are my options?
This is a good, fairly complete walkthrough of one particular setup - its for ubuntu but most of it should carry forward well enough for debian. That particular guide hints at quotas but dosen't seem to impliment them so you'd need to check. elsewise it covers nearly everything you asked for
Here you can find some information about Email Services. It is from the Ubuntu server guide, but maybe this can help you.