This class executes the second stage of message transformation to be sent through the list. This stage is
put after storing messages into archive spool (See also Sympa::Spindle::DistributeMessage).
Transformation processes by this class are done in the following order:
• Executes "post_archive" hook of message hooks if available.
• Adds / modifies "Reply-To" header field, if "reply_to_header" list option is enabled.
• Adds / overwrites following header fields:
"X-Loop"
"X-Sequence"
"Errors-To"
"Precedence"
"Sender"
"X-no-archive"
• Adds header fields specified by "custom_header" list configuration parameter, if any.
• Adds RFC 2919 "List-Id" field, RFC 2369 fields (according to "rfc2369_header_fields" list
configuration option) and RFC 5064 "Archived-At" field (if archiving is enabled).
• Removes header fields specified by "remove_outgoing_headers" list configuration parameter, if any.
Then this class passes the message to the last stage of transformation, Sympa::Spindle::ToList.