With Postfix, the whole process is controlled by four configuration
default_verp_delimiters (default value: +=)
What VERP delimiter characters Postfix uses when VERP
style delivery is requested but no explicit delimiters are
verp_delimiter_filter (default: -+=)
What characters Postfix accepts as VERP delimiter
characters on the sendmail command line and in SMTP commands.
Many characters must not be used as VERP delimiter characters,
either because they already have a special meaning in email
addresses (such as the @ or the %), because they are used as
part of a username or domain name (such as alphanumerics), or
because they are non-ASCII or control characters. And who
knows, some characters may tickle bugs in vulnerable software,
and we would not want that to happen.
smtpd_authorized_verp_clients (default value: none)
What SMTP clients are allowed to request VERP style
delivery. The Postfix QMQP server uses its own access control
mechanism, and local submission (via /usr/sbin/sendmail etc.)
is always authorized. To authorize a host, list its name, IP
address, subnet (net/mask) or parent .domain.
With Postfix versions 1.1 and 2.0, this parameter is called
authorized_verp_clients (default: $
disable_verp_bounces (default: no)
if Postfix sends one bounce report for multi-recipient
VERP mail, or one bounce report per recipient. The default,
one per recipient, is what ezmlm needs.