On 21 Oct 2016, at 6:57, Volker Cordes wrote:
Hello,
I have a domain where all mail is stored in a single mailbox and then
being fetched by a zarafa server via pop3. The zarafa server of course
has to be able to deliver the mails to the correct users. So I tried
adding X-Envelope-To via check_recipient_access which is working as
long
as there only is one recipient.
This is an intrinsically flawed design. The fact that it mostly works
and has been done by many people for many years can't fix the
misapplication of POP3 to the role of intermediate mail transport.
With mulitiple recipients (to, cc and bcc fields) for each recipient
address a X-Envelope-To header is generated and the mail is delivered
once for every recipient into the catchall mailbox. Is it possible to
change this behaviour so that there is only one X-Envelope-To header
in
every delivered mail?
smtpd_recipient_limit=1
The primary risk of that setting is due to the fact that some SMTP
clients do not properly handle a 4xx response to the 2nd-nth RCPTs,
which is how Postfix enforces the policy. 99.99% of the multi-recipient
messages will get delivered, possibly with the additional recipients
delayed substantially, but some tiny fraction will not get retried by
sending systems and another tiny fraction will simply fail at the first
4xx and be retried with all recipients until the client gives up.
