Rewrite To/From Addresses

Discussion regarding the Standard version.
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Joined: Wed Jun 20, 2018 5:16 pm

Rewrite To/From Addresses

Post by magnified » Wed Jun 20, 2018 5:21 pm

As we work through our project plan to Migrate our internal Exchange email to Office 365, we are also working on doing some cleanup of our environment.

Our On-Prem Exchange hosts about 180 employee mailboxes - but it was also used a notification system for customer-equipment by utilizing Exchange Based/public facing distribution lists and contacts. This was another case of "its only temporarily" many years ago and it now contains 1000 contacts and about 500 distribution lists.

This configuration polutes our GAL, complicates the Exchange Instance and is just plain dirty. My end-goal is to have a Hybrid O365 configuration to facilitate printers/ADSync/Easy Mailbox Moves etc. I'd love to carve this piece out of the equation and have it run off its own server.

There are about 250 pieces of customer equipment, all with SMTP Server settings pointing to our Exchange Instance using mail settings like below. Based on DNS I can redirect this equipments SMTP traffic to the new server - piece of cake.

SMTP Server: --> Exchange:25
SMTP From:

It is almost impossible for us to connect to each of the customer-based pieces of equipment to change the settings, so, I've been working on a solution that would allow us to handle the migration on the server side best we can.

In a test environment, I've setup MailEnable Standard with groups and members. I set rhe primary domain for this server is set to "", but I've added an alias to the system to allow mail to be accepted from our equipment "".

This works - the mail lands into the MailEnable server and the members are notified by means of the distribution list.

Problem is: Because the equipment dictates the "From Address" ( - any bouncebacks/replies/SPF checks are all related to the primary domain name (which will eventually be O365), and not the secondary domain I've stood up for the equipment.

I'd love some kind of way to do a rewrite of the FROM & TO address on reciept to change the addresses from to and properly setup SPF etc on this new domain.

That said, I've been developing in C# for 10 years - there is likely SMTP Server Source code out there someway that we can rework to create a relay/proxy and do the address conversions - or some kind of event handler in some free/commercial SMTP Package that would allow us to fix up the addresses.

Is there an option or feature available in Standard/Pro/Enterprise that allow me to modify or force the addresses to be from my secondary domain?

Appreciate the help.

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