imap configuration

[steve%prd.co.uk@localhost (Steve Blinkhorn)]

I have the need to configure my mail servers to accept remote mail
from company smartphones, which will have unpredictable IP addresses
at any given time.

As I understand it, this is best done using port 587 and a suitably
configured imapd, but it is not clear to me whether stock imapd can do
the job.  I get the impression that I need to build something like
dovecot - but what is the difference between dovecot and dovecot2?

I guess this is all obvious once you know it, but if there's a "how to
get started with port 587" guide, that would be really helpful.

-- 
Steve Blinkhorn <steve%prd.co.uk@localhost>