A mail account on an external host can collect messages directed to all Accounts (users) of your Domain. The RPOP Module can be instructed to retrieve mail from such an account and distribute it to the local users.
When a message is sent via the Internet, the information about the sender and the message recipients is sent in the so-called mail envelope. If mail is sent via SMTP, the envelope is sent as a sequence of protocol commands.
The information in the envelope is usually the same as the information in the message header fields, but it is not always true. The most important exceptions are:
When a message is stored in a mailbox, the envelope information about the sender is added to the message headers as the Return-Path header field. Usually, the envelope information about the recipients is not added to the message headers.
When the RPOP Module retrieves a message from a Unified Domain-Wide Account, it has to recompose the message envelope and deliver the message to its final recipient. If the message contains the Return-Path header field, the address in that field is placed in the new envelope as the sender's address, and the header field is removed from the message (it will be recreated when the message is delivered to its final destination).
If a Unified Domain-Wide Account is created with the mail system that can copy the recipient addresses from the envelope into some message header field, then the delivery via RPOP is as reliable as SMTP delivery. Enter the name of that header field into the Unified Account RPOP record settings, and the RPOP Module will look for that field in all messages retrieved from that account. The addresses from that field will be placed into the new envelope and the messages will be directed to those addresses. The header field itself is removed from the message. All accepted addresses get the 'report on failure' flags, so if message delivery fails, the original message sender (the address in the message Return-Path field) will receive an error report.
Unified Domain-Wide Accounts can be provided with a CommuniGate Pro Server running on the provider side. For messages stored in those accounts, the envelope recipients are added to the message headers as the X-Real-To fields. To learn how to provide Unified Domain-Wide Accounts with CommuniGate Pro, check the Local Delivery Module section.
A legacy sendmail system can be configured to add X-Real-To header fields, too. See the Appendix A below.
RPOP records for Unified Domain-Wide Accounts should be created for the postmaster Account in the Main Domain.
The WebAdmin RPOP page for this Account contains the Special field:
Special: The name of the messages header (RFC822) field that the provider host inserts into the messages stored in the Unified Domain-