On 17 Jul 2015, at 9:17, Tony Stocker wrote:
Quick background, we recently shifted from a very old mail server
running
Postfix (~2.2.10) to a newer, though not cutting edge, one also
running
Postfix (~2.6.6). As much as practical the configuration files from
the
old server were used to provision the new server. For the most part
everything seems to be working normally.
However we have one oddity that we've noticed so far. We have several
systems that use 'uuencode' and 'mailx' to send reports through the
mail
server, the basic format of the cron job that does these is like so:
/usr/bin/uuencode
"/logs/system/reports/${system}/ftpreport.${yesterday}"
"${system}.ftpreport.${yesterday}" | /bin/mailx -s "FTP Report
${yesterday}
${system}" astocker
These worked fine with the old server, the emails would arrive and
have a
file attachment, appropriately named
'"${system}.ftpreport.${yesterday}"'.
However the new server does not appear to be "attaching" the file to
the
email, but instead outputting the uuencode directly to the mail body.
You seem to be unfamiliar with how "attachments" in email work.
All "attachments" in email are blobs of text directly in the body of
messages, formatted and encoded in ways that are understood by MUAs
(Mail User Agents, i.e. mail clients) to be "attached" files distinct
from the parts of the message that are human-readable with less complex
interpretation. Normal MTAs (Mail Transport Agents, i.e. mail servers)
know nothing of attachments and do nothing with them other than
transport the blobs of text without reformatting except in a few edge
cases, and then in ways that don't damage standard types of attachment
encoding.
The uuencode/uudecode pair of programs is the oldest means of encoding
files for mail transport and decoding mail to extract "attached" files.
They predate any carefully-crafted standards for email attachments and
the 3 (at least) entirely independent implementations on Unix-like
systems mostly interoperate well. The cron job you run literally just
dumps the output of uuencode into the body of a mail message sent by
mailx. The last thing to modify the message is mailx. On the other end,
you apparently use a MUA that recognizes some flavors of
uuencode-piped-to-mail messages as having an "attached" file. That's not
simple to do reliably, and in fact many users of Outlook have been
mystified over the years by it's overeager interpretation of lines like
'begin [digits] [characters]' as the start of an attachment: mystified
and occasionally pranked. Because the uuencode-piped-to-mail format is
not really very consistent (due to varying behaviors of various
uuencode's and mail/Mail/nail/mailx's) many MUAs wisely don't try to
interpret it, instead only supporting the well-specified standard
mechanisms under the "MIME" umbrella for attaching files to mail and
recognizing attached files in mail.
So your best solution is to stop using the best of the 80's mail
software for sending files via mail and move into the 90's by using
something that generates MIME attachments instead of relying on some
fuzzy heuristics in a particular MUA to recognize uucode blobs as
attached files.
