I have recently set-up a dovecot + postfix + maia + roundcube server in a jail which is working very nicely. Let me know here what is the status of your deployment and I will probably be able to help if you are still stuck somewhere.
I know this is not the main point of your post, but, to send mail from your host you can do the following:
Running make in /etc/mail creates a bunch of .cf and .mc files with your hostname as basename
, change 127.0.0.1 to your jail's ip
run make again and replace submit.cf
with the resulting your_hostname.submit.cf
mv /etc/mail/submit.cf /etc/mail/submit.cf.orig
mv your_hostname.submit.cf submit.cf
You should now be able to send mail via postfix, using mail
at the host's command line (or from any other jail where you have done the above).
mail -v firstname.lastname@example.org