POP3 Collector is a freeware utility that downloads email from one or more POP3 mailboxes and forwards them to an SMTP server (tested against Exchange). This piece of software will collect e-mail messages from multiple POP3 mailboxes and forward them to the SMTP server of choice.

POP3 Collector Features:
1. 1.2.7: added debug window so that you can see how POP Collector is analysing the received messages. It is available from the Tools menu, and you can load either an archived email (from POP Collector), or a raw message saved from another program. When you click Analyse, all details read from the message by POP Collector are displayed.
2. IMPORTANT BUGFIX 1.2.7: A bug has been identified that meant recipient email addresses weren't being parsed correctly. This affected email addresses containing an underscore, and possibly a few other characters. This bug has now been fixed, you are strongly advised to upgrade to the latest version.
3. IMPORTANT BUGFIX 1.2.6: This release fixes an issue with mail retention on systems with a system locale set to other than US or UK. Mail will now be retained or deleted properly independent of locale.
4. Due to several requests, the main window is now resizable, which means that the log viewer can be expanded to show more information.
5. Collect now and suspend all collection options added. You can suspend all collection while editing settings, and trigger a collection as needed to test an account (Collect Now overrides the suspension status).
6. Context menu added to configuration menu (right-click now brings up available options).
7. Supports global mailbox (with failsafe). You can use a catch-all mailbox with your ISP to collect all the mail for your domain. It will be sent to the correct recipient by POP Collector (except when recipient is in BCC field, which is not included in email headers).
8. Unlimited POP3 email account support (maximum supported accounts is entirely dependent upon your operating hardware).
9. Multiple domain support. You can download email from as many domains as you like.
10. All settings are customizeable per POP3 mailbox. You can check the POP3 mailbox at any interval starting from 1 second (though this is HIGHLY inadvisable).
11. Each POP account can have it's own SMTP server. POP Collector can now act as a router between many email systems.
12. SMTP AUTH support (currently AUTH LOGIN, further methods may be added on request).
13. Message validity checking. Optionally you can enable (per POP mailbox) the checking of each downloaded message to ensure it is compliant with RFCs. In some (few) cases POP servers return slightly malformed mail, which an SMTP server may or may not handle correctly. Any header lines that are not compliant are removed.
14. Messages will be retained on the POP server until successful delivery or a permanent error (5.x.x) is reported by the SMTP server. A notable flaw in the SBS POP connector is that it in the event that server hard-disk space runs out, it will actually delete mail from the POP mailbox even though it can't be delivered to the Exchange server.
15. Messages can be kept on the server for any length of time after successful delivery.
16. Mail archive facility. All received mail (whether successfully forwarded or not) can be stored to a folder. This is disabled by default, as the folder can get very large if not monitored (POP Collector currently does no checking of this folder).
17. Will run as a service on Windows 2003 or XP. So long as Windows 2003 Resource Kit Tools are available (specifically InstSrv and SrvAny - these tools also work on Windows XP), POP Collector can now automatically install itself as a service (available from the Tools menu). When loading the UI to configure POP Collector, the service will automatically be stopped, and then restarted once the UI is closed.
18. Full logging with automatic (and configurable) checking of log file sizes.

The license of this software is Freeware, you can free download and free use this email checker software.