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The RPOP Module can be used when the CommuniGate Pro Server has a dial-up connection with dynamically assigned IP address, and thus the Server cannot receive mail via SMTP. The RPOP Module polls the specified remote host (ISP) accounts, retrieves messages and stores them in the Server mailboxes.
Users with several mail accounts on several systems can instruct the RPOP Module to poll those accounts, so all their mail is collected in their CommuniGate Pro Account.
The RPOP Module supports Unified Domain-Wide accounts. A Domain-wide account is an account on the ISP or any other host that collects all messages sent to your Domain. The RPOP Module retrieves all messages from such an account and distributes them based on the addressing information in the message header fields. The RPOP Module can poll several Unified Domain-Wide accounts.
The RPOP Module activity can be limited using the TCP Activity Schedule. The Module does not poll any remote account till the TCP Activity Schedule allows the Server to initiate outgoing network connections.
Use the WebAdmin Interface to configure the RPOP Module. Open the Mail pages in the Settings realm, then open the RPOP pages.
Click the Update button to modify the RPOP Module settings.
If an Account has the CanModifyRPOP setting enabled, the Account user can modify the Account RPOP records via using the WebUser Interface, or a XIMSS client.
To remove an RPOP record, set its polling period value to Never.
To create a new RPOP record, enter its name in the last table row and select some valid polling period value.
Click the Update button to modify the RPOP record set.
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:
The RPOP Module will search for all To:, Cc:, and Bcc: header fields in retrieved messages. It will use the addresses from those header fields only if that address is routed to any existing local CommuniGate Pro Account.
If an address is routed to the SMTP or some other Module, or an address cannot be routed at all (unknown user name error, etc.), the RPOP Module does not send any error messages to the sender. The Module simply ignores that address.
All accepted addresses get the 'do not report failures' flags, so if the message delivery fails for any reason, no error report is sent to the original message sender.
If none of the message To:, Cc:, or Bcc: addresses has been accepted, the RPOP Module sends that message to the postmaster Account in the Main Domain.
As explained above, the method based on To:/Cc: header field parsing can cause problems when the actual envelope addresses are not the same as the header field addresses. Besides, some systems do not process the Unified Accounts correctly, so if a message is sent to three users in your domain, those systems may store three copies of the message in the Unified Domain-Wide Account Mailbox. Since each message header contains the addresses of all three users, the RPOP Module will deliver three copies of the message to each user.
The problems with Bcc, mailing lists, and duplicated message can be very annoying, so we strongly recommend you to ensure that the provider's mail system adds the envelope information to the messages stored in your Unified Domain-Wide Account, and you can use the Special Header Field feature.
The following file can be used to force the freeware sendmail program to store the envelope information in message headers.
After these updates are applied, make sure that sendmail delivers all mail for your domain to one account on the sendmail system. The sendmail configuration for that unified account should list the 'mailer' marked with the 'T' flag.