Re: sendmail newbie question

From: Matthew Seaman (m.seaman_at_infracaninophile.co.uk)
Date: 11/30/03

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    Date: Sun, 30 Nov 2003 09:14:32 +0000
To: Marty Landman <MLandman@face2interface.com>

    On Sat, Nov 29, 2003 at 08:36:57PM -0500, Marty Landman wrote:

    [Problems sending mail...]

    > In a moment. First I'll say what I do know:
    >
    > - there is a /var/mail/Marty, empty
    > - emails to Marty go to root's mailbox with the message "user unknown"
    >
    > I don't know much. :)
    >
    > I did sendmails to localuser@SwamiSalami and Marty@SwamiSalami and this is
    > what appended to /var/log/maillog

    Try changing your user account to 'marty' -- all lower case. Use
    vipw(8) to do that. In general under Unix, usernames are almost
    always all lower case and so are most host and domainnames.

    The problem is that sendmail(8) [ or any standards compliant MTA ]
    expects e-mail addresses to be case insensitive. The DNS copes pretty
    well with the host part -- if you look carefully, you'll see that the
    FreeBSD mailer uses '...@FreeBSD.org' and '...@freebsd.org' pretty
    much interchangeably. In fact, sendmail(8) will always match
    domainnames case insensitively, but will preserve the case of any
    addresses it processes.

    The tricky part is the username -- here sendmail just passes the
    username through in whatever case it gets *except* when it does final
    delivery (ie. when it passes the message to the local delivery agent).
    At that point, it maps the username to lowercase -- for historical
    reasons: when sendmail started out there were mail systems that didn't
    understand the distinction between lower case and upper case at all,
    and the addresses on e-mails passing through those systems would get
    case folded. However on unix systems, user 'Marty' is not
    automatically the same as user 'marty' or as user 'MARTY'. Such
    systems have long since vanished from the net, but I have a sneaking
    suspicion that even nowadays some windows mailers may decide that they
    "know best" how to capitalise names and will silently "correct" them
    for you.

    It is possible to set up sendmail to preserve the case of usernames
    but doing so would mean your mail system wouldn't be standards
    compliant, so I'll keep quiet on the issue -- unless anyone really
    does have a burning desire to know how?

            Cheers,

            Matthew 

    -- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP: http://www.infracaninophile.co.uk/pgpkey         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK

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