Name
default_verp_delimiters
Possible values:
characters
Default:
+=
VERP is a technique used with mailing lists to handle bounced
messages. It combines the list owner address and original recipient
address with a special delimiter character. The default_verp_delimiters parameter specifies which characters to use when
constructing VERP return addresses.
Example:
default_verp_delimiters = +=