Re: first stab at simple mailer

[Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>]

    * Do not embed newlines in strings.  Just use string concactenation:

	"abcd\n"
	"efgh\n"
	"..."

	^^ this is treated as a single string in C

    * Background the process using the daemon(3) function

    * Wrap calloc, malloc, strdup, etc.

    * I didn't quite undersand what the link() business was about.  When
      processing queues, it is best to avoid all unnecessary namespace
      manipulation (rename, link primarily).

    * Remote delivery, which you have as 'XXX implement me'...  you need
      to be able to sort by the target domain's MX lookup and you need to
      do MX backoff & forwarding for any remote delivery.  It isn't too
      bad but DNS lookups can be difficult to implement efficiently.

    * Configuration file. Yup. you need one :-).

    How serious are you about this?  There are a number of issues that
    would have to be addressed, even for a simple mailer.  Handoffs for
    .forward files (including processing exit codes properly), supporting
    /etc/mail/aliases and /etc/mail/virtusertable, and handling a more
    sophisticated local delivery check (using a DNS lookup on the target 
    domain to see if its a CNAME to the actual host, or something similar)....
    all are absolutely required.

    There are many other issues as well, including mail size limitations,
    smarter queueing mechanisms (sorting by target recipient to prevent a
    stalled target host from stalling the entire queue), handling
    out-of-disk-space issues gracefully, etc.

    If you intend to build the daemon side as well then there are many
    other issues as well including limiting the memory used to hold headers,
    proper string parsing, hand-off security, MIME issues, and other things.

    please, no more SGID binaries.  Just make the front-end connect to 
    the back-end over a localhost socket and pass creds with sendmsg() 
    and SCM_CREDS (with regards to a mail.local equivallent).

						-Matt