Attachments and MIME processing channel options

A number of channel options affect the processing of so-called attachments and MIME parts. (Note that these are channel options which can generally be set on anytype of channel. See also Message conversions for optional, more complex, processing of attachments and MIME parts, sometimes involving a "hop" through the specialized Conversion channel.)

See also:
 * conditionalpassthrough Option
 * conditionalrelay Option
 * conditionalsecuritymultiparts Option
 * convert_octet_stream Option
 * convertoctetstream Option
 * defragment Option
 * ignoreencoding Option
 * ignoremessageencoding Option
 * ignoremultipartencoding Option
 * inner Option
 * noinner Option
 * sourceinner Option
 * nosourceinner Option
 * interpretencoding Option
 * interpretmessageencoding Option
 * interpretmultipartencoding Option
 * limitheadertermination Option
 * relaxheadertermination Option
 * linelength Option
 * maxblocks Option
 * maxlines Option
 * msexchange Option
 * nameparameterlengthlimit Option
 * noconvert_octet_stream Option
 * noconvertoctetstream Option
 * nodefragment Option
 * nomsexchange Option
 * nothurman Option
 * parameterformatdefault Option
 * parameterformatminimizeencoded Option
 * parameterformatstripencoded Option
 * parameterlengthlimit Option
 * processsecuritymultiparts Option
 * retainsecuritymultiparts Option
 * nouma Option
 * passthrough Option
 * relay Option
 * thurman Option
 * uma Option
 * Message conversions
 * Conversion channel
 * Functional group list of channel options