Change MX records and switch spam filters without losing email
Change MX records and switch spam filter providers without losing email: lower TTLs, stage the new path, cut over, verify, roll back.
5 guides
How do you decommission your old spam filter after switching?
After moving to a new spam filter, remove the old one cleanly: MX, SPF includes, connectors, gateway IPs, ARC sealers, DKIM keys, smart hosts and firewall rules.
9 min read Switching & migrationHow does DNS TTL affect an MX record change?
What DNS TTL means, why propagation is really caching, when to lower TTL before an MX or SPF change, how negative caching works, and how to check what resolvers see.
9 min read Switching & migrationExchange Server 2016 and 2019 end of support: what are your options?
Exchange Server 2016 and 2019 left support in October 2025 and paid ESUs end in October 2026. Compare Exchange SE, Exchange Online and hybrid, and plan filtering.
10 min read Switching & migrationHow to change MX records without losing email
A cutover checklist for MX changes: lower TTL, stage the new destination, keep the old server accepting mail, verify with headers and roll back cleanly.
11 min read Switching & migrationHow to switch spam filter providers without a gap in protection
Move from one MX spam filter to another: export lists, keep quarantine access, run both connectors during overlap, change MX and remove the old service.
9 min readAbout these guides
Changing where your mail is delivered is routine, but it is one of the few email changes that can lose messages if it's rushed. When you change MX records, resolvers keep the old answer until its TTL expires, so for a while some senders deliver to the old destination and some to the new one. Both have to accept and deliver mail during that overlap.
These guides cover the two situations businesses meet most often:
- Changing MX records for any reason: lowering the TTL first, keeping the old destination working, checking the change from outside, and rolling back if something goes wrong.
- Switching spam filter providers: running the old and new filters side by side, moving allow and block lists, handling messages still in the old quarantine, and when to cancel the old service.
A safe switch follows the same checklist every time:
- Write down your current MX, SPF and DMARC records so you can roll back.
- Lower the MX record's TTL at least a day ahead.
- Set up the new destination and test it before you change DNS.
- Change MX, then confirm it with an MX Lookup and a test message from an outside account.
- Keep the old service accepting mail until the old TTL, and any retries from sending servers, have run out.
If you're moving to iBlockSpam, the switching page explains what the guided setup does, including the before/after DNS comparison and rollback steps.
Frequently asked questions
Should I cancel my old spam filter before or after changing MX?
After. Keep the old service accepting mail until the old MX record's TTL has expired and you've seen mail arriving through the new filter for a few days. Senders that cached the old record, or are retrying earlier failures, may still deliver there. Export your allow and block lists before the old account closes.
Do I need to tell users before switching spam filters?
Their mailboxes, addresses and mail apps don't change, but do tell them about anything they'll see differently: a new quarantine digest email, a new way to release held mail, or a new place to report missed messages. A short note stops the new digest being mistaken for phishing.
When should I schedule an MX change?
Pick a quiet period when someone can watch mail for a few hours afterwards, such as early in the working week rather than late on a Friday. Lower the TTL the day before. Avoid times when critical mail is expected, like a payment run or a filing deadline, in case you need to roll back.