I want to move our SMTP services in house, but have a major hurdle I need to overcome. Our firewall/content filter has an SMTP mail scanner blacklists, virus etc. The system is supposed to be device based, but they change the rules up here and the policy IMO is quite abusive. For the email based services it is per email address. We have people that have multiple email boxes i.e. customerservice@ claims@ shipping@ receiving@, sales people have addresses at our web domain as well as our internal 'retail' domain that is used for correspondence with our vendors we also have a few email addresses associated with our company's blog site. salespeople that have left also have messages that get forwarded to other sales people. The final gotcha is our catch-all boxes, this gets looked at daily and there are always messages. So an exact count out the number of email addresses is not possible.

I will have a offsite spooler service for protection when our internet or mail server is down but have not decided on anything so if there is one that does something that would accomplish this in any manner I am open to it. I need to modify the recipient address and put it in the X-Apparently-To header (adding it if needed). I can handle the message being delivered properly on the back end.

I'm not sure exactly what to call what I need, I can run the pre-processor in house as well and forward its output through the firewall. The catch-all account is the problem it will cause us to exceed the license and will nearly triple the cost of the firewall.

Being able to make a list of valid incoming recipient email addresses to leave untouched and replacing the recipient address with catchall@domain.com would work but it would be nice to be able to undo it after the firewall processes it so the email can be forwarded out of the catch all box more readily.

  • Is the license based on email headers or RCPT TO -command? If it is based on RCPT it should be easy to change RCPT TO <whatever@example.com> into RCPT TO <catchall@example.com> without changing any headers at all. – Esa Jokinen Mar 6 '15 at 6:03

If you can't make the business case you might want to reconsider moving the SMTP services completely in-house:

Decide on a primary e-mail domain, run that in-house and leave all other domains on an external mailhost where you map those secondary e-mail addresses to "real" mailboxes on your primary domain.
The exact method depends a bit on the mailserver software, but both postfix and sendmail support such virtual mappings.

bob@example.org, alice-who-left@example.org & bob.smith@example.blog all get forwarded over SMTP to bob@example.com and you incur only a license fee for Bob's actual mailbox bob@example.com.

Alternatively if you don't have a business case for using the SMTP scanning features of your firewall, then reconsider that product or by-pass and disable it.

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