Configuring Autoforward Sender Address

Customer would like to have auto forwarding feature as described below:

• Scenario: (User A -> User B (Auto forwarder) -> User C)

1. B@example2.com is a user at customer.
2. An email is sent from A@example1.com to B@example2.com
3. B@example2.com set an auto-forward rule so emails are being forwarded to C@example3.com automatically.
4. C@example3.com received the forwarded mail.

• Current behavior : The mail received by C@example3.com has mail from header A@example1.com

  (i.e. the mail from is unchanged by client when forwarding to user C)

• Requested behavior : The mail received by C@example3.com has mail from header B@example2.com

  (i.e. the mail from has been changed by user B when forwarding to user C, so the mail looks like as if it was originally sent by user B)

• Reason for the request : Currently, the mails being auto forwarded by user B are occasionally get failed to pass SPF check somewhere in the path, which will result that the mail cannot be forwarded to user C.

Solution

The following is an example of what the Sieve config and rules could look like:

dovecot.conf

plugin {
  # Use editheader
  sieve_extensions = +editheader
}

Sieve Rule

require "editheader";
require "variables";
require "envelope";

# ... Any other rules

# Obtain the user's full email address somehow
# It can be obtained from the recipient address (without full name)
# An alternative is to put the primary address into the script as a literal.
if envelope :matches "to" "*" { set "user_email" "${1}"; }

# This part of the script MUST be the final rule, otherwise other rules are
# affected since the message is modified.

# Drop the original "From:" header
deleteheader "from";

# Add a new "From:" header
addheader "From" "${user_email}";

redirect "forward@example.com";

Note

It is very important to make that deleteheader, addheader, redirect the last rule in the sieve script, as this would affect other actions as well.