Headertrailingpreserve, headertrailingremove Channel Options

Trailing spaces on header lines
The  and   channel options, applicable on source channels, control whether the MTA strips (removes) trailing white space from the ends of physical header lines.

By default the MTA removes trailing white space from the ends of physical header lines; this means both from the ends of logical (unfolded) header lines, and from the ends of folded portions (physical lines) of a single (logical) header line.

The  channel option may be used to instead preserve such trailing white space. This may be of particular interest for folded header lines, when it is desired to preserve original, "interior" white space in the logical (unfolded) header line. It is also typically used in conjunction with the  channel option.

See also:
 * headerfoldpreserve Option
 * Headers channel options
 * Channel options