Although it was my intention that v4.73 be the last in the v4.x family of Mercury versions, at a certain point it became clear that there needed to be another update to fix a variety of small problems before beginning the migration to version 5. V4.74 contains over 40 small fixes, and two rather more significant corrections: a problem where messages deleted by IMAP-based clients were not actually deleted and reappeared on the next connection has been fixed; and an issue where a site had more than 3 MX mail servers declared but the first three were all unavailable (which could cause Mercury to attempt to connect to the wrong host for delivery) has also been addressed.
It's also worth noting that the Mercury installer and executable files are now digitally signed, using my name ("David Harris"). If your browser or installer complains about them being unsigned, or tells you that they have been signed with a signature that does not use my name, then the files are not authentic. A small security measure, but we believe it is quite worthwhile.