IMAP Migration Checklist for Teams

IMAP migration is boring on purpose: same folders on two servers until counts match. Teams get burned when someone resets a password mid-job, when Sent never copies, or when MX flips while the migrator is still on Inbox 40%.

Use this checklist whether you are entering MailShrine from cPanel, Google Workspace, Microsoft 365, or another IMAP host.

Real-life example: Ledger & Line

Amaka migrates accounting firm Ledger & Line (11 mailboxes, ~180 GB total). She scheduled a Thursday night run, pasted passwords into a migrator sheet, and walked away. Two FAICPA logins had MFA prompts overnight — those seats finished at 12%. Friday morning looked “done” until partners asked where last year’s audit threads went.

Her fix: per-seat owner sign-off, not a single green progress bar.

Phase 0 — Decide ownership

Related: zero-loss cutover.

Phase 1 — Inventory (do not skip)

• Spreadsheet of every address (mailbox / alias / forward / shared)Not completed
• Approximate mailbox size and VIP flagNot completed
• Source IMAP hostname, ports, SSL requirementsNot completed
• Destination IMAP settings from MailShrine (client settings)Not completed
• Plan seats: Free = 1 mailbox + 2 aliases — buy seats before sync if you need moreNot completed

Provider-specific notes: cPanel · Google · Microsoft

Phase 2 — Access that survives overnight

• MFA path documented per VIPNot completed
• Temporary “migration” passwords stored in a vault, rotated after cutoverNot completed
• Migrator retries + logging enabledNot completed

Phase 3 — Destination ready

• Domain added in MailShrineNot completed
• Mailboxes created with matching local partsNot completed
• Aliases mapped (alias vs mailbox)Not completed
• Webmail login tested for each seatNot completed
• MX still on the old host while phase 4 runsNot completed

Phase 4 — Copy & verify

Run order that saves pain:

1. Pilot 1–2 non-critical seats end-to-end.
2. Full cohort overnight.
3. Delta / catch-up the morning of DNS day.

Per-mailbox verification table

• Pilot signed offNot completed
• Full sync completeNot completed
• Delta scheduledNot completed
• VIPs manually spot-checkedNot completed

Phase 5 — Cutover coordination

• MX TTL lowered 24–72h priorNot completed
• Staff told when to stop sending from old profilesNot completed
• MX published to MailShrine (MX guide)Not completed
• SPF/DKIM updated (SPF, DKIM)Not completed
• External test messages per critical addressNot completed
• Devices rebuilt same dayNot completed
• Old host watched for stragglers (timeline)Not completed

Propagation reference: DNS timing.

Phase 6 — Close-out

• Migration passwords rotated to final secrets + 2FANot completed
• Migrator credentials revokedNot completed
• Old IMAP disabled only after quiet periodNot completed
• Postmortem notes for next hire waveNot completed

Failure codes Amaka now watches

1. Green bar, empty Sent — tool excluded Sent by default.
2. One user forever retrying — MFA prompt invisible overnight.
3. Folder name collisions — source had INBOX/invoices vs Invoices.
4. Early MX — new mail arrives on MailShrine while history job still thrashing the network.

Next steps

• Migrate without losing mail · MX cutover timeline · Outlook setup after move

Citations & References

• Reference: RFC 3501 — INTERNET MESSAGE ACCESS PROTOCOL — VERSION 4rev1
• Reference: Microsoft Learn: IMAP migration
• Reference: Google: Migrate email from IMAP servers

Written by Marcus T., Technical Program Manager. Marcus turns mailbox migrations into checklists owners can actually finish.