There is also a case with public key.

Limit personalization: Only when posted from WWSympa, entire text will be converted. Otherwise only footer/header will be converted.

As of Postfix 2.3, Content of Return-Path: pseudo-header field added by pipe(8) for null envelope sender became "MAILER-DAEMON".  Empty `null_sender` option will prevent this behavior.
As a workaround, the uppercase "<MAILER-DAEMON>" will be treated as null envelope sender.

Recommended file name won't be decoded with earlier version of MIME-tools.

Unreasonable error message to notify broken signature in the message, if the messages signed with PGP/MIME was posted.

In some cases, a message will start with a multipart/related including a multipart/alternative; In that case, with the current code the multipart/related was urlized as a 'msg.0.bin' attachment, which was wrong.
Fixing this behaviour by:
1- allowing to go down two levels of multiparts
2- preventing any urlization if the part is not included in a 'multipart/mixed' parent to prevent urlizing the content of multipart/related or multipart/alternative.

Following suggestion by reviewer @ikedas: Replacing 'get()' by 'mime_attr()' and, therefore, a regular expression by 'eq'.

1- message text was treated as attachment and remained on the server as either "msg.0.bin" or "msg.0.txt" files. Fixed by testing the part type before urlizing it.
2- some special characters in message id led to the attachment to be considered missing by Sympa.

I had to refactor the code a bit to allow urlizing of nested multiparts.

The detail of urlization treatment is as follows:

1- any multipart/mixed message part will be analyzed to look for urlizable parts,
2- any mulitpart/related message part will be be analyzed to look for multiârt/mixed sub parts,
3- within the multipart/mixed parts, any text/* part whose "Content-Disposition" header is not "attachment" and has a correct Content-Type.charset value is kept untouched,
4- any other subpart is kept on the server an replaced by a download link.

By this change, "sp" along with "p" in DNS TXT RR will be supported.

[-change] DMARC: Net::DNS is required when dmarc_protection.mode is neither all, dkim_signature, domain_regex nor none.

Mail::DKIM::Signer wraps DKIM-Signature with with \r\n\t; this
is the hardcoded Separator passed to Mail::DKIM::TextWrap via
Mail::DKIM::KeyValueList. MIME::Tools on the other hand
(MIME::Head::stringify() in particular) encode EOL as plain \n;
it is thus necessary to normalize CRLF->LF for DKIM-Signature to
avoid confusing the mail agent.

Fixed by parsing the field according to standards.

Fixes:

  - Message footer/header files of domain/site default are put in `mail_tt2` subdirectories while those of list config are not.
    Fixed by put all of them in consistent location without intermediate directories (See also Notes below).
  - Entries for header/footer files in `edit_list.conf` were ignored.

Changes:

  - File names themselves of header/footer were changed:
    `message_header`, `message_header.mime` etc.
    This is due to concideration about conflict between files and directories with domain names (See also Notes below).
  - Header/footer files with `.mime` extension:
    Previously, files with this extension were always preferred, then files without extension were used.  This behavior has not been documented.
    Now files with extension will be searched only in case `footer_type` is `mime`.  Files without extension will be searched in both cases.

Notes:

  - Files with older names/paths in list/domain/site config directories will be copied to new location during upgrading process.
  - Template files with old names in families (`message.header.tt2` etc.) will be used as before and will be copied to new location during instantiation. If files with new names (`message_header.tt2` etc.) will be preferred, if they will be added.

Known bug:

  - There are no web UI to edit global footer (`message_global_footer`).