Workstream 01
Confirm the source platform before choosing a method
An address hosted by a web provider might be traditional IMAP, hosted Exchange, or a Microsoft 365 tenant administered through a reseller. Those setups have very different migration and licensing options.
Record the source host, supported protocols, administrator access, mailbox count, approximate sizes, aliases, forwarding and any archive or shared-inbox behaviour. Ask whether users have an Outlook desktop archive that is not stored on the server.
| Expectation | IMAP alone | Additional work to scope |
|---|---|---|
| Historical email and folders | Usually relevant | Folder mapping, limits and exception checking |
| Contacts and address books | Not part of IMAP | Export/import or separate migration method |
| Calendars and meeting rooms | Not part of IMAP | Calendar migration and resource recreation |
| Shared mailbox delegation | Not established by IMAP copy | Permissions, account and workflow design |
| Mobile and Outlook profiles | Not delivered by data transfer | Device inventory, setup and training |
Workstream 02
Separate data movement from mail-flow cutover
Mail can be pre-staged before the destination becomes authoritative, but the last synchronisation and DNS cutover still require coordination. Inventory existing MX, SPF, DKIM and DMARC records, plus application senders, before replacing any values.
Test external and internal mail routes, old aliases and forwarding after cutover. A message arriving in a single test inbox does not establish that all the company's systems are now sending correctly.
Workstream 03
Agree what “complete” means
Write acceptance tests around mailbox search, expected folders, archive access, aliases and users’ ability to sign in on their actual devices. Where unsupported items remain, list them plainly rather than hiding them in a migration tool’s summary.
For businesses with large PST archives or complex Outlook delegation, separate that remediation from the base IMAP project so both parties know the real price and schedule.
What to capture before the decision
- Source protocol verified, not inferred from hosting brand
- Mailboxes, sizes, aliases and shared identities listed
- Calendars and contacts explicitly included or excluded
- DNS/mail authentication inventoried
- Device setup, acceptance and aftercare agreed
Workstream 04
IMAP migration boundaries buyers often mistake for an all-in service
IMAP transfers email messages from accessible folders; it is not a migration of calendars, address books, Outlook rules, delegated identities, shared mailbox rights, distribution groups or identity policies. Ask the provider whether source folders are mapped cleanly, whether the source supports required authentication and whether server throttling, message sizes or retention rules affect the copy. If the old server has no reliable administrative access, pilot viability may be limited.
The cutover and the migration are separate activities. Document mailbox aliases, authentication records, outbound application senders and the expected coexistence period. A mailbox can report a completed copy while messages still arrive at the old host if DNS and routing have not been switched and checked from outside the organisation.
| What the buyer expects | IMAP generally covers? | Separate workstream |
|---|---|---|
| Historical email and folders | Subject to source access and tool limits | Folder and message reconciliation |
| Calendars and contacts | No | Export, recreate or use another supported connector |
| Shared mailboxes and delegates | Not as permissions | Provision and validate target access |
| Mobile profiles, aliases and app SMTP | No | Client setup, DNS and application-sender inventory |
Workstream 05
A practical reconciliation test for a hosted-mail move
Before copying, record source mailbox folder counts and representative old, large, flagged and attachment-heavy messages. After cutover, have selected users search for a known message, open the attachment, send a message outside the organisation, receive a reply and verify the reply routes back to Microsoft 365. Note which folders were excluded deliberately and which need manual treatment.
If the service is sold by mailbox count, require the quote to state data assumptions, number of client devices, post-cutover support hours and whether calendaring or shared permissions are separately charged. A low headline price is not a substitute for acceptance criteria.
What to capture before the decision
- Confirm source protocol and sign-in method are supported
- Check file size, folder names and throttling on a pilot mailbox
- Inventory aliases, forwarding and all SMTP applications
- Test external sending, reply routing and authentication after cutover
- Agree how long the source remains accessible
Use an IMAP migration when the boundary is understood. Don't use it as a substitute for discovering everything else your team relies on.
Source documents and limitations
These references establish current vendor behaviour; they do not verify an individual customer's configuration or imply Microsoft affiliation. Technical claims should be rechecked before execution.