How do I enable users to retrieve e-mail from the Internet when all e-mail is relayed through an Internet server

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Problem: How do I enable users to retrieve e-mail from the Internet when all e-mail is relayed through an Internet server to an e-mail server behind a firewall on Open Server 5.0.x?

Solution: Using figure-1:


Fig. 1

Machine a.x.com is a fully configured machine on the Internet with a valid Internet IP address and is configured with an Intranet IP address.
Machine b.x.com is configured with an Intranet IP address on the same subnet as the Internet server’s Intranet IP.
All e-mail is relayed to b.x.com from the Internet through a.x.com.  b.x.com is setup to handle all local e-mail traffic via DH in sendmail.

Ensure the user that will be retrieving e-mail from the Internet has either a valid account on b.x.com OR has an alias pointing to user@a.x.com in the /usr/lib/mail/aliases file on b.x.com and a valid account on a.x.com.  In each instance the account can be a real account through the Account Manager or a pseudo account created through the Internet Manager.

To enable access perform the following:

  1. If the user exists on b.x.com add a .foward file to their home directory with the following line:
    user@a.x.com
    replacing the word user with the user’s real account name on a.x.com.
  2. Add the user’s account name to the /usr/lib/sendmail.cf class L rule, CL, on a.x.com to enable local delivery of e-mail even though there is a relay.
  3. Create an alias for the user on a.x.com with the following line:
    user:    user
    Where the first instance of the user’s name is the user on b.x.com, (The user’s e-mail address), and the second instance is the username on a.x.com (the users pop account/IMAP name).
    If using Open Server 5.0.5 and above make sure release supplement 5.0.5a or greater is installed and you run the ‘newaliases’ command to install the aliases.
  4. Add a .forward in the users home directory on b.x.com if the user is a real user.  If the user is a pseudo user, (Created using the Internet Manager), then create an alias on b.x.com in the /usr/lib/mail/aliases file (run ‘newaliases’ and ensure 5.0.5a or better is installed).

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