The filter keyword may be used on the native and ims-ms channels to specify the location of user filter files for that channel. It takes a required URL argument describing the filter file location. nofilter is the default and means that a user mailbox filters are not enabled for the channel.
The sourcefilter and destinationfilter keywords may be used on general MTA channels to specify a channel-level filter to apply to incoming and outgoing messages, respectively. These keywords take a required URL argument describing the channel filter file location. nosourcefilter and nodestinationfilter are the defaults and mean that no channel mailbox filter is enabled for either direction of the channel.
The obsolete channelfilter and nochannelfilter keywords are synonyms for destinationfilter and nodestinationfilter, respectively.
The fileinto keyword, currently supported only for the ims-ms and LMTP channels, specifies how to alter an address when a mailbox filter fileinto operator is applied. For ims-ms channels, the usual usage is:
The above specifies that the folder name should be inserted as a sub-address into the original address, replacing any originally present sub-address.
For LMTP channels, the usual usage is:
where $4O is a 4 and the letter O, not the number zero.
Note that for fileinto to work with LMTP, the tcp_lmtpss channel on the backend message store requires the flagtransfer keyword. (see 16.5.1 To Configure Back End Stores with LMTP and a Minimal MTA).