Hi,
I'm looking for a new solution to solve a problem that was formerly
properly solved with UUCP over TLS for the last 15 years, but since UUCP
is really stone aged and not supported anymore, I'm looking for a
solution and didn't find one.
Given Problem:
A server nachine with postfix running at a hoster with permant
connectivity, acting as a regular (virtual) MX receiver for a lot of
domains.
For some domains, the postfix should forward all (high volume) traffic
for these domains (not just particular addresses) to other machines
(private machines at homes of users) that
* are occasionally powered on only, can be down for up to two months,
still must not lose mails,
* have dynamic IP-Adresses (DynDNS possible, but addresses can change
any time, and DynDNS not really synchronous)
* are behind firewalls, thus not reachable from Internet
* thus need to pull mails
uucp+rbsmtp solved that problem for many years, but simply are not
maintained anymore for more than a decade.
* Simply delivering mails into a mailbox and fetching with pop3 works
for simple addresses, but not for domains and multiple addresses
(envelope missing)
* There is a „multidrop” method to spool mail for multiple recipients
into a single pop3 box, but I didn't find a documented way to do
this with postfix, instead lots of comments from people having
trouble with it and considering it as not reliable.
* One consideration is to use ETRN, but this wouldn't work directly
and reliably (dynamic ip addresses and not reachable from Internet
due to firewall restrictions)
* Another consideration is to use ETRN, but over a VPN network, thus
giving machines a pseudo-static IP-Address, but this is some
overhead and would require to configure postfix with a queue timeout
of 2 months
* Next consideration is the same as above, but with two postfix
instances, to have one with short timeout to keep the queue to the
internet short (<1week) and the other one long (>2months), but this
is even more overhead and not exactly what an MTA is made for.
* There's a LMTP-to-AMQP-tool, which theoretically solves exactly that
problem, but AMQP nodes are typically not made for such huge amounts
of data, and typically have proprietary file formats, thus no way to
debug or repair in case of failure.
* I'm considering to mimic UUCP with modern methods, i.e. store the
mails as files with envelope (i.e. smtp commands as rbsmtp did) in a
directory and give pull access over a REST API (or simply WEBDAV),
and have a small daemon at the target machines, frequently looking
for new files and fetching them, which seems to be the most simple
and reliable method, but that's homebrewn.
is there a known, proven, and stable (and, in contrast to UUCP, modern
and maintained) method to solve this problem?
regards
Hadmut
