Non-MIME Binary Attachment Conversion

Mail in certain non-standard (non-MIME) formats; for example, mail in certain proprietary formats or mail from the Microsoft Mail (MSMAIL) SMTP gateway is automatically converted into MIME format if CHARSET-CONVERSION is enabled for any of the channels involved in handling the message. If you have a tcp_local channel then it is normally the incoming channel for messages from a Microsoft Mail SMTP gateway, and the following will enable the conversion of messages delivered to your local users:

CHARSET-CONVERSION  

  IN-CHAN=tcp_local;OUT-CHAN=ims-ms;CONVERT         Yes

You may also wish to add entries for channels to other local mail systems. For instance, an entry for the tcp_internal channel:

CHARSET-CONVERSION

  IN-CHAN=tcp_local;OUT-CHAN=l;CONVERT              Yes
  IN-CHAN=tcp_local;OUT-CHAN=tcp_internal;CONVERT   Yes

Alternatively, to cover every channel you can simply specify OUT-CHAN=* instead of OUT-CHAN=ims-ms. However, this may bring about an increase in message processing overhead as all messages coming in the tcp_local channel will now be scrutinized instead of just those bound to specific channels.

More importantly, such indiscriminate conversions might place your system in the dubious and frowned upon position of converting messages—not necessarily your own site’s—which are merely passing through your system, a situation in which you should merely be acting as a transport and not necessarily altering anything beyond the message envelope and related transport information.

To convert MIME into the format Microsoft Mail SMTP gateway understands, use a separate channel in your MTA configuration for the Microsoft Mail SMTP gateway; for example, tcp_msmail, and put the following in the mappings. file:

CHARSET-CONVERSION  

  IN-CHAN=*;OUT-CHAN=tcp_msmail;CONVERT        RFC1154