So, a couple of updates since last or last-er:
Using mailx to send a mail with attachment:
mailx -m -r sender_user@example.org -s "Subject header" -a /file/to/attach.log receiver_user@example.org
With uuencode to attach a file:
uuencode <source_file> <target_file> | mailx -m -r sender_user@example.org -s "Subject header" receiver_user@example.org
With mutt to attach a file:
echo "This is the message body" | mutt -a "/file/to/attach.log" -s "Subject header" -- receiver_user@example.org