By default, PMDF preserves the case of addresses as originally presented to PMDF. Since UNIX accounts are case-sensitive, it is important that the mailbox of an address be in the correct case when delivering to a UNIX account. Sites with a consistent account name convention---all accounts being lowercase for instance---can want to use case insensitive matching when delivering to local mailboxes.

PMDF rewrite rules can be used to forcibly control the case of addresses going to the local channel (or any other channel), for instance, to force all local mailboxes to lowercase; see Section 2.2.5.4.

If the case of the user accounts is not regular, an alternate approach is to use PMDF aliases to achieve case insensitive matching. Note that PMDF alias matching is case-insensitive, but the case of the expanded alias is preserved. Thus for instance the use of an alias

adam: AdAm

would mean that messages to any of adam, Adam, ADAM, aDAm, etc., would be delivered to the account "AdAm".