Am 26.10.20 um 11:24 schrieb R. Diez:
Hello R, I only wrote about the incoming side - of course, you also
want to
send mail to remote users, and that includes users with an address of
…@myisp.com. They will go to the ISP and be fetched to local from there.
That is not what I had in mind. My users will not go to the ISP and
fetch their e-mails from there. They will always go to my internal mail
server. If a user is on the road, he/she will connect with OpenVPN first.
Probably I could have said that better: fetchmail will fetch those mails
from the ISP, same as any other mails to some...@your.site - the Inbox
at your ISPs will always be empty, your users will only interact with
the dovecot instance on premise. There is some inefficiency, the price
for a simpler setup.
I have seen Microsoft Exchange setups that carried on working locally if
the Internet connection was down. If Microsoft can do that, I want to
have it too. 8-)
With some tinkering, you can configure your local relay smtp to
deliver those locally,
To be more clear - if you have a local smtpd too (not just dovecot and
fetchmail, postfix perhaps), that sits between your users MUA and your
ISPs smtpd, you can make it recognise some...@your.site as a "local"
account and have those mails delivered locally. You have to set up some
mappings though, that replicate the ones in your fetchmailrc.
Start of a HOWTO:
1) Install dovecot, create virtual accounts for all of your users
2) Install fetchmail, make it pull the ISPs IMAP and deliver locally
3) Install postfix as a smart relay and deliver locally to locals
Feel free to fill in the details ;)
--
peter
