Use a transport map for sites that don't grok VERP-style sender addresses, and use smtp_generic_maps to strip off the VERP portion.
UNTESTED example: /etc/postfix/master.cf: # NO WHITESPACE in name=value smtp-no-verp unix - - n - - smtp -o smtp_generic_maps=pcre:/etc/postfix/no-verp.pcre /etc/postfix/main.cf: transport_maps = hash:/etc/postfix/transport /etc/postfix/transport: example.com smtp-no-verp: /etc/postfix/no-verp.pcre: /^([^+]+).*(@example\.net)$/ $1$2 The tricky part is the PCRE pattern. Except for "example" and "net", everything else must remain unchanged. Wietse