I am looking into setting up my web server to have its own IMAP/POP/SMTP server. For the IMAP and POP3 and I am using Dovecot and the webmail I am using Horde. Its all mostly working, I can connect to the imap and pop server, and I can send emails, and horde shows the emails in the inbox. The problem I am having is at the moment there seems to be a bit of a disconnect between between Horde and Dovecot. At the moment, if I create a new user inside horde, before they can give the inbox, I first of all need log in to my web server and create a user using useradd, specifying the directory, creating the Maildir directory within the home user directory and set the password for the account. What I am wanting to do, instead of having to do multiple different steps, e.g. create user in horde, create user in linux, I want it all to be done together, i.e. I create the user in horde, and I don't need to do anything else, the inbox directory is all created without needing to do anything else. 
Dovecot Authentication with MySQL and Horde Webmail
dovecot;imap;webmail