Inventory before touching DNS
Export or record every domain, alias, destination, catch-all rule and sending identity. Note any address that routes to multiple people.
Move from ImprovMX to MailerZ without guessing.
A reversible, test-first runbook for changing email routing while protecting the messages your business depends on.
The non-negotiable rule
Do not delete the old provider or its routing configuration before DNS caches have expired and all critical aliases pass inbound and outbound tests.
Build the same routes in MailerZ
Add the domain, create named aliases first, set destinations, choose unknown-recipient behavior and invite only the seats that need access.
Publish verification and sending records
Add the exact TXT, DKIM and other authentication records shown in MailerZ. Do not publish a second SPF record at the same name.
Test outbound SMTP
Configure one client or application with the generated MailerZ credential. Send externally and verify From, reply path and delivery history.
Plan the MX cutover
Lower TTL in advance if appropriate. During the change window, replace the old MX records with the exact MailerZ hosts and priorities.
Test real inbound paths
Send to named aliases, a multi-destination alias and an unknown address. Confirm the expected hold or forward behavior.
Monitor before removing the old account
Watch both systems for the length of the previous MX TTL plus a safety window. Keep your configuration inventory until results are stable.
Know the way back before you switch.
Keep the previous MX values in a secure change record.
If critical mail fails, restore the previous MX set exactly.
Remember that rollback also follows DNS TTL and cache behavior.
Preserve MailerZ delivery evidence for support diagnosis.
Ready to configure the destination?
Use the interactive planner first, then create the MailerZ routes without touching the existing MX records.
Create the destination