This article describes what our Mail Filter Redirection (MFR) tool is and how it works.
We use the Mail Filter Redirector during Smarsh Hosted Services's Onboarding process to avoid DNS propagation issues at the time of cutover.
The MFR tool sits on the perimeter of the Smarsh Hosted Services network and routes any mail sent to Smarsh Hosted Services for your account back to your legacy server. Using Mail Filter Redirection lowers the impact of changing your MX records on mail flow. As the new MX records propagate, mail sent to the old record will route back to the legacy server and mail sent to Smarsh Hosted Services will also be sent back to the legacy server. Once the new MX records have propagated fully all mail flows through Smarsh Hosted Services before going back to the legacy server.
It is crucial not to make any MX record changes until Mail Filter Redirection is enabled.
Once the MFR is in place, change your MX record prior to cutover to point to Smarsh Hosted Services. The MFR will stay in that configuration for at least three days (72 hours) while the DNS record change propagates to all the DNS servers around the world. After MFR is enabled and MX records are switched to Smarsh Hosted Services and fully propagated, users continue receiving mail in their legacy mailboxes.
At the time of cutover the Mail Filter Redirection will be disabled and mail starts flowing to Smarsh Hosted Services server within a short period of time.
If you are using a mail filter such as MX Logic or a Barracuda and will be removing it from your infrastructure, we recommend adding the IP addresses of our Mail Filter Redirector to the whitelist to prevent any interruption in mail flow during the migration. Please contact Support for the IP ranges.
Important: The Mail Filter Redirection will only forward email for addresses that exist on Smarsh Hosted Services account including company contacts, distribution lists and mail-enabled public folders. If you have changed the naming convention for your email addresses you must add the old address as an alias for the user. If there is an address not being migrated over to Smarsh Hosted Services, this address will no longer receive mail once the mail filter redirection is in place and MX records are switched.
Mail flow and cutover with MFR enabled:
Mail flow and cutover with no MFR in place: