One large factor for me deciding to migrate to dovecot's lda ('deliver')
is to use SIEVE, which is under active development and is likely to
become a standard (imho). I see no point in creating another lda.
Yeah, with SIEVE support being found in Kmail and addons or plugins for
thunderbird and probably others...it kinda paves the way for a standard eh?
What I do see is a need for vpopmail to be able to give 'deliver' any
data it needs to do its job (for instance maildir or mailbox,
destination location, etc). At some point vpopmail might also include
providing SIEVE filtering rules.
The only problem I see at this point in time is how dependent vpopmail
is on others to make use of it. vpopmail started out as something to
fill out a need missing in the qmail toolchains. Even then, qmail did
not have everything (eg: no imap) and it is really nice that dovecot
added vpopmail support especially since Sam dropped vpopmail support
from courier toolchains.
If vpopmail can take things a bit beyond just say single system user and
perhaps be able to handle 1) multi system user virtual domains and 2)
massive multi system user management with an appropriate backend like
pgsql, then I hope there is incentive for the dovecot guys to keep their
relationship with vpopmail and not try to come up with their own
Right now, postfix + dovecot + vpopmail looks pretty neat without
getting too many different libraries/frameworks involved. If this can be
taken a step further...