Prior to running the PMDF Mailbox Servers configuration utility you must have installed PMDF-MTA on your system, and it is recommended that you also configure PMDF itself (and the PMDF Service Dispatcher, normally done automatically as part of the PMDF configuration) before configuring the PMDF POP and IMAP mailbox servers. Refer to Chapter 1 if you have not already installed and configured PMDF-MTA.

If you were previously using non-PMDF servers, then you will need to shut down and disable such servers before you can use PMDF's multithreaded servers. (Before configuring PMDF's servers is a convenient time to do this, although if you prefer you can wait until after you have configured PMDF's servers but before you try to start PMDF's servers.)

The PMDF POP and IMAP mailbox servers configuration utility will prompt for several pieces of information. In particular, it will ask which POP and/or IMAP servers you want to run, and how many simultaneous POP connections and how many simultaneous IMAP connections you want to allow at your site, to which you will need to provide site-appropriate answers. For further questions, the configuration utility attempts to provide reasonable default values. You may want to mostly take the default answers the first time you configure, and then later after observing the actual POP and IMAP usage at your site, reconfigure with answers geared for your site. Configuration questions will include the following:

• Whether you want to run the legacy mailbox POP server, or the MessageStore mailbox POP server, (or neither).
• Whether you want to run the legacy mailbox IMAP server, or the MessageStore mailbox IMAP server, (or neither).
• Whether you want to log POP and IMAP connections.
• Whether you want to run a POPPASSD server to support changing passwords from POP clients using the ad-hoc password changing mechanism used by, for instance, Eudora. Note that the POPPASSD protocol involves sending both the old and the new password "in the clear", a point to be considered carefully when deciding whether or not to provide this service.
• Whether you want to enable PMDF's password changing web CGI.
• If you select use of the MessageStore IMAP server or MessageStore POP server, the utility will also configure the PMDF MessageStore and PMDF popstore for you and will therefore present several configuration questions regarding the MessageStore and popstore. These questions will include the following.
  1. What is the pseudo domain name assigned to the MessageStore. This is the domain name which will be used to address mail to PMDF MessageStore users. For instance, if you want MessageStore users to have addresses of the form user@msgstore.naples.example.com, you would use the domain name msgstore.naples.example.com for the MessageStore.
  2. The local postmaster address.
  3. The default primary message storage quota to allow each user. The default account is granted this quota. When you create user accounts, they will be given this primary quota unless you specify a different quota. A primary quota value of 0 grants unlimited storage quota.
  4. The default overdraft message storage quota to allow each user. This is the amount by which users are allowed to exceed their primary quota.¹ The default account is granted this overdraft quota which is then used as a default setting for user accounts you create.
  5. How many days to retain PMDF popstore messages, awaiting user download. If a user has not deleted a message after this limit, it is either deleted silently or returned to its originator as unread. To retain messages indefinitely, specify an age limit of 0.
  6. A special account name for posting to public folders in the MessageStore.
• If you chose to run a POP server, there are a few POP server configuration questions, including:
  1. What is the maximum number of simultaneous POP connections you want to support on your system. Note that this is not the total number of users or even total number of POP users; rather, it is the maximum number of POP users whose POP clients will be connecting simultaneously. Also note that POP connections are typically brief: the POP client connects, downloads messages, and disconnects. Choose a number that will provide reasonable access for your users without overburdening your system resources.
  2. What is the maximum number of connections you want to allow per server process. To support a given number of simultaneous connections, there is a tradeoff between the number of processes used and the number of connections handled per process. Fewer connections per process tends to result in greater responsiveness for the individual connections, but the resulting need for more processes incurs greater system overhead. A moderate number of connections per process is usually best.
  3. Whether you want the server to support the POP3 UIDL command. The UIDL command permits POP clients to keep track of messages by an identifier. POP users who enable "leave mail on server" behavior typically appreciate having UIDL supported, as it can allow their client to keep track of which of the messages in their inbox they have actually already read. Sites that want to discourage "leave mail on server" behavior may want to disable UIDL support.
• If you chose to run an IMAP server, there are a few IMAP server questions, including:
  1. What is the maximum number of simultaneous IMAP connections you want to support on your system. Note that this is not the total number of users or even total number of IMAP users; rather, it is the maximum number of simultaneous IMAP connections. Some IMAP clients make (and keep open) more than one connection to the server. So the number of simultaneous IMAP connections may be higher than the number of simultaneous IMAP users. Unlike POP connections, IMAP connections tend to be long lasting: the IMAP client connects and stays connected as the IMAP user reads and moves messages between folders. Choose a number that will provide reasonable access for your users without overburdening your system resources.
  2. What is the maximum number of connections you want to allow per server process. To support a given number of simultaneous connections, there is a tradeoff between the number of processes used and the number of connections handled per process. Fewer connections per process tends to result in greater responsiveness for the individual connections, but the resulting need for more processes incurs greater system overhead. A moderate number of connections per process is usually best.