LMTP client TCPIP channels

LMTP client TCP/IP channels
In the MTA&#x27;s implementation of LMTP, an LMTP client channel is a specially configured TCP/IP channel. At its most basic, any outbound TCP/IP channel configured with the    channel option is an LMTP client channel. However, additional channel options should also be set upon an LMTP client channel; see the example in Typical TCP/IP channels and servers.

In the Messaging Server implementation, the intended design is that, to the greatest extent possible, message processing (including address canonicalization,  spam/virus filter package processing,  user Sieve filter application, defragmentation of MIME message fragments,  any content conversion implemented via the conversion channel, etc.),  will be applied on the "front end" MTAs during (or prior to) enqueue to a   channel. (Then the LMTP server on the back end Message Store host need merely insert the already-entirely-pre-digested message into the Message Store.)  In particular:



 In a typical LMTP configuration, various address transformations resulting from the interpretation of the  MTA option and coordinating LMTP-oriented rewrite rules are usually best handled by setting the   and   channel options on   channels. 

 Various TCP/IP or LMTP protocol relevant channel options, e.g.,  and , are commonly set. 

 To ensure MIME defragmentation of any messages destined via LMTP to the Message Store, the    channel option should be set on the   channels. 

 And so that application of Sieve filters on the "front end" MTAs will properly convey any intended " " action effects back to the back end LMTP server, the   channel option should be set on the   channel(s). 

 (The MTA&#x27;s LMTP implementation also makes use of proprietary LMTP extensions to convey other important information from the LMTP client to the LMTP server, including quota data and IMAP flag Sieve effects; the MTA&#x27;s LMTP server and LMTP client negotiate the extension use and send this information automatically.) 



In the MTA implementation, the LMTP client channel code is the SMTP client channel code, merely configured specially: the many channel options and  TCP/IP-channel-specific options affecting SMTP client operation may also be set and affect LMTP client operation. (Note that this in contrast to the MTA&#x27;s LMTP server, which consists of distinct and separate code from the SMTP server, so configuration options for the SMTP server do not always have LMTP server counterparts.)

See also:
 * lmtp Option
 * multigate Option
 * connectcanonical Option
 * fileinto Option
 * port Option
 * single_sys Option
 * Conversion channel
 * Defragmentation channel
 * Typical TCPIP channels and servers
 * TCPIP-channel-specific options
 * LMTP back end TCPIP channel
 * LMTP channels