Switching hosts

Inventory first

• Export the full DNS zone: A, AAAA, CNAME, MX, TXT (SPF, verification records), CAA, SRV.
• Find DKIM selectors (s= in a sent email’s DKIM-Signature header), then dig TXT [selector]._domainkey.example.com.
• Run dig +short MX example.com and dig TXT _dmarc.example.com. Know where mail lives.
• List subdomains, cron jobs, server redirects and anything outside WordPress in the web root.
• Record PHP version and extensions (php -v, php -m), memory limit and upload size.

Prepare the new host

• Lower TTL on records you will change to 300 seconds, at least one old TTL ahead (24 to 48 hours).
• Take a full backup of files and database and store it off both servers.
• Match or improve the PHP version and extensions on the new server.
• Copy files, import the database. Domain or path changed? wp search-replace with --dry-run first.
• Recreate cron jobs and any server-level redirects or rules.

Rehearse before DNS

• Point your hosts file at the new IP and test the site on its real domain.
• Test logins, forms, search, checkout, uploads and wp-admin on the new server.
• Have SSL ready: DNS validation, a copied certificate, or issuance within minutes of cutover.
• Freeze content changes, or plan a final database sync just before cutover.

Cut over

• Change only A/AAAA and website CNAMEs. Leave MX and mail records alone unless mail moves.
• Moving DNS hosts too? Recreate every record and compare zones before changing nameservers.
• Check dig +short example.com @8.8.8.8 and the authoritative nameservers.
• Confirm a valid certificate, the expected 200/301 codes via curl -I, and purge all caches and CDN.

After the move

• Send test mail to two major providers. SPF, DKIM and DMARC must pass. Add the new server to SPF if it sends mail.
• Watch logs and Search Console for 404s and errors for a week. Confirm new backups run.
• Keep the old host for at least 7 days, until its logs show no more traffic.
• Raise TTL back (3600 is common). Take a final backup, then cancel the old host last.