1.1 --- a/ch03.roff	Fri Jun 01 12:42:52 2012 +0200
     1.2 +++ b/ch03.roff	Fri Jun 01 15:33:37 2012 +0200
     1.3 @@ -9,8 +9,6 @@
     1.4  
     1.5  .H1 "Stream-lining
     1.6  
     1.7 -
     1.8 -.H2 "Removal of non-MUA Tools
     1.9  .P
    1.10  MH had been considered an all-in-one system for mail handling.
    1.11  The community around nmh has a similar understanding.
    1.12 @@ -31,6 +29,120 @@
    1.13  available resources should be concentrated at the point where MH is
    1.14  most unique. This is clearly the MUA part.
    1.15  .P
    1.16 +The goal for mmh was to remove peripheral parts and stream-line
    1.17 +it for the MUA task.
    1.18 +
    1.19 +
    1.20 +.H2 "Removal of Mail Transfer Facilities
    1.21 +.P
    1.22 +In contrast to nmh, which also provides mail submission and mail retrieval
    1.23 +facilities, mmh is a MUA only.
    1.24 +.P
    1.25 +The MSA is called ``Message Transfer Service'' (MTS) in nmh.
    1.26 +The facility establishes TCP/IP connections and speaks SMTP to submit
    1.27 +messages for relay to the outside world.
    1.28 +This part is implemented in the
    1.29 +.Pn post
    1.30 +command.
    1.31 +Demanded by the changes in
    1.32 +emailing, this part of nmh required changes in the last years.
    1.33 +Encrypted connections needed to be supported, hence SASL was introduced
    1.34 +into nmh. This added complexity to the nmh without improving it in
    1.35 +its core functions. Also, keeping up with recent developments in
    1.36 +this field needs requires development power and specialists.
    1.37 +Mmh cuts this whole facility off and depends on an external MTA instead.
    1.38 +The only outgoing interface available to mmh is the
    1.39 +.Pn sendmail
    1.40 +command.
    1.41 +Almost any MTA provides a
    1.42 +.Pn sendmail
    1.43 +command.
    1.44 +It not, any program can be substituted if it reads the
    1.45 +message from the standard input, extracts the recipient addresses
    1.46 +from the message header and does not conflict
    1.47 +with sendmail-specific command line arguments.
    1.48 +.P
    1.49 +To retrieve mail, the
    1.50 +.Pn inc
    1.51 +command in nmh has the ability to establish TCP/IP connections
    1.52 +and speaks POP3 to retrieve mail from remote servers.
    1.53 +As with mail submission, here encrypted connections are required
    1.54 +today, thus SASL support was added.
    1.55 +As POP3 is superseded by IMAP more and more, support for message
    1.56 +retrieval through IMAP will become necessary to be added soon.
    1.57 +Mmh has no support for retrieving mail from remote locations.
    1.58 +It depends on an external tool to cover this task.
    1.59 +There are two ways for messages to enter mmh's mail storage:
    1.60 +Incorporate them with
    1.61 +.Pn inc
    1.62 +from the system maildrop, or with
    1.63 +.Pn rcvstore
    1.64 +from the standard input.
    1.65 +.P
    1.66 +In consequence, mmh includes neither networking nor SASL code anymore.
    1.67 +Two large separate functional units are removed.
    1.68 +They account for about XXX lines of code and XXX libraries.
    1.69 +.P
    1.70 +With the removal of the MSA and MRA, mmh converted from an all-in-one
    1.71 +mail system to the core: the MUA.
    1.72 +Following the Unix philosophy, it focuses on one job and to do that well.
    1.73 +Now, of course, mmh depends on third-party software.
    1.74 +An external MTA/MSA is required to transfer mail to the outside world;
    1.75 +an external MRA is required to retrieve mail from remote machines.
    1.76 +There exist excellent implementations of such software,
    1.77 +which do this specific task likely much better than the internal
    1.78 +versions of nmh do it. Also, this provides the choice for the best
    1.79 +suiting one of the available implementation.
    1.80 +.P
    1.81 +As it had already been possible to use an external MSA or MRA,
    1.82 +why not keep the internal version for convenience?
    1.83 +If this would question the sense in having a fall-back pager in all
    1.84 +the command line tools, in case
    1.85 +.Pn more
    1.86 +or
    1.87 +.Pn less
    1.88 +wouldn't be available, the answer is intuitively seen.
    1.89 +Now, an MSA or MRA is clearly more complex than a text pager, but
    1.90 +still the concept holds: If programs become complex, split them;
    1.91 +if projects become complex, split them.
    1.92 +Complexity is demanded by the problem to solve. Decades ago,
    1.93 +emailing had been small and simple.
    1.94 +(Remember,
    1.95 +.Pn /bin/mail
    1.96 +had once covered anything there was to email.)
    1.97 +As the complexity in emailing increased, MH remainded mostly unchanged.
    1.98 +Nontheless, in nmh the POP server, which the original MH had included,
    1.99 +was removed. Now is the time to take one step further and remove
   1.100 +the MSA and MRA.
   1.101 +Not only does it decrease the code amount of the project,
   1.102 +but more important, it removes the whole field of message transfer
   1.103 +with all its implications from the project.
   1.104 +.P
   1.105 +Users of MH are usually able to set up an external MSA and MRA.
   1.106 +Also, the popular MSAs and MRAs have large communities and a lot
   1.107 +of documentation available.
   1.108 +.P
   1.109 +Choices for MSAs range from the full-featured
   1.110 +.I Postfix
   1.111 +over mid-size solutions like
   1.112 +.I masqmail
   1.113 +and
   1.114 +.I dma
   1.115 +to small forwarders like
   1.116 +.I ssmtp
   1.117 +and
   1.118 +.I nullmailer .
   1.119 +Choices for MRAs include
   1.120 +.I fetchmail ,
   1.121 +.I getmail ,
   1.122 +.I mpop
   1.123 +and
   1.124 +.I fdm .
   1.125 +
   1.126 +
   1.127 +
   1.128 +.H2 "Removal of non-MUA Tools
   1.129 +.P
   1.130  Several of nmh's tools were removed from mmh because they didn't
   1.131  match the main focus of adding to the MUA's task.
   1.132  .P
   1.133 @@ -99,9 +211,6 @@
   1.134  .Pn wmh ,
   1.135  saved more than 7\|000 lines of C code \(en a major achievement.
   1.136  
   1.137 -.U2 "Removal of the MTS
   1.138 -.P
   1.139 -
   1.140  
   1.141  .H2 "mhshow show Merge
   1.142  .P