The AddHeader statement requires the full header line in one continuous string, in the format

AddHeader "<full header line>"

• If the header line is present:
  • It will be replaced if an alternative value is specified.
  • It will be removed if no value is specified.
• If the specified header is not already present, it will be inserted at the end of the headers.
• AddHeader should not be used where the header name may appear more than once (e.g. “Received: …”).

From VPOP3 v6.20 onwards, the header modifier format has been extended:

• If you prefix it with -, it will be added at the the start of the final headers
• If you prefix it with +, it will be added at the end of the final headers
• If you prefix it (after the -/+ above) with “{”<username>“}” (eg {bob}Subject: Bob's new subject ) it will only be added to the headers when placed into that user's mailbox
• If you prefix it with #, it will remove the header if the data matches the regular expression specified in the modifier's data - eg #Bibble: ^[a-z]{5}$ - otherwise the original header will be left in place

Changing the subject header

AddHeader "subject: VPOP3SPAM ${Subject}"

Removing a header line, by not setting a value

AddHeader "X-MyHeader:"

Changing the value of a header, or inserting it if it does not already exist

AddHeader "X-MyHeader: The new value of the header named X-MyHeader"