Understanding Tenant Migrations
With today's proliferation of always-available, cloud-based email providers, why would you need a backup MX service? The answer has to do with the fact that email itself is that modern email routing and delivery still relies on a standard written in 1986.In order for an email you send to make its way to a recipient's mail server, special DNS records (MX records) are used to determine how the email should be routed. Multiple MX records can be used to provide backup email destinations, ordered by lowest preference.
24 Hour Outages?!?!
If your email provider's platform is unavailable for some reason, or undergoing maintenance, emails delivered per the MX records can be delayed, or fail and bounce back to the sender (this behaviour can vary greatly between email platforms).
Some organizations may only use a single MX record (pointing to Office365, for example), while others may use multiple MX records indicating alternate servers with the same email provider (i.e. Google Suite).
A backup MX service can be used as a permanent "destination-of-last-resort", allowing emails to queue (and not bounce) when the destinations which would normally be used are unavailable. Once this configuration is setup, it requires no further maintenance, and simply provides an additional level of redundancy and control in the event of a provider outage.
Avoid email loss while migrating between Office365 tenants
A common use case involves the transition between (or within) email providers. For example, Microsoft's guide to migrating email accounts between Office365 tenants includes the following instruction:
Change your primary MX record from Office 365 to domain that is not reachable, i.e. "unreachable.example.com". Internet mail servers attempting to deliver new mail will queue the mail and attempt redelivery for 24 hours. Using this method, some email may return a non-delivery report (NDR) depending on the server attempting to deliver the email. If this is a problem use an MX record backup service. There are many third party services that will queue your email for days or weeks. Once your migration is complete, these services will deliver the queued mail to your new Office 365 tenant.
If non-delivered email is unacceptable, our backup MX service can be employed to temporarily queue all emails during the tenant transitionGet Started
We completed the simultaneous migration of 9 tenants after our company merged. Updating the DNS and then watching the emails queuing and waiting for our server to come online was the easiest part of our migration.
Your product worked really well, thanks very much! I will be sure to come back next time we have this situation. Thanks for all your assistance.
As far as your team is concerned went everything worked as expected. As far as the project overall – there of course always are a few twists on something this size, most of which just required some adjustments on our side. But thank you for your hand holding and support.
We had some very specific requirements. Thank you for your cheat sheet and reminder about the TTL on our MX record. It made the migration quite a bit faster.