DNS TTLs and the art of the zero-downtime cutover
Most migration downtime is self-inflicted and comes down to TTLs set wrong, set too late, or set on the wrong records. Here is how caching actually behaves and how to plan a cutover around it.
Migration
Migrating your client book without a single angry phone call
Fifty sites, fifty DNS zones, hundreds of mailboxes — and one imagined catastrophe. A well-run migration is a checklist executed in a sensible order. Here is the checklist, and what to demand from the host receiving it.
Migrating mailboxes with imapsync — a practical runbook
Moving mailboxes between providers without losing mail, flags or folder structure. The imapsync invocations we actually use, the flags that matter, and how to sequence a cutover.