Email archive migration · Customer-hosted

Simply DiscoverMigration

Your archive.
Your next destination.

Move historical email with a plan for where it lands, visibility into what needs attention, and a record of the outcome. From the first mailbox to the final handover.

Follow the migration

Collection. Delivery. An account of both.

01
Destination choice
Mailbox, archive or portable output.
02
Controlled execution
Scope, schedule and recover work.
03
Accountable handover
Outcomes, exceptions and reports.

A move worth planning

Change the platform.
Keep sight of the email.

Simply Discover Migration is customer-hosted email archive migration software for IT teams, migration specialists and organisations changing how they store historical mail.

Collect from supported sources such as Mimecast and Microsoft 365. Deliver to a supported mailbox, archive or file destination, or retain the content in Simply Discover. Follow discovery, collection and export separately, with mailbox-level investigation and reporting.

A familiar migration brief

“Our archive agreement is ending. Recent mail needs to stay easy to find. Older correspondence belongs in the archive. And we need to explain anything that did not arrive.”

An illustrative project, not a customer testimonial. Here is how the work can be organised.

01
Agree the destination.
Choose the output and mailbox placement. Review identities, provisioning and what successful delivery means for that route.
02
Set the boundary.
Select mailboxes, domains and dates. Test connections, review mappings and create the migration ready to run or held for a controlled start.
03
Work through the move.
Monitor collection and export. Inspect exceptions, retry eligible work and keep successful progress in view.
04
Reconcile the outcome.
Review finished items alongside skipped, failed and outstanding work. Prepare the reports and destination evidence for sign-off.

01 / Choose where it belongs

An archive move.
More than one way forward.

Microsoft 365, Proofpoint, a destination Mimecast tenant, portable files or Simply Discover itself. Choose a supported route around how the organisation needs to use the content.

Mailbox & In-Place Archive

Email where people expect it.

Deliver eligible historical email into Microsoft 365 active mailboxes or In-Place Archives, with reviewed source-to-target mailbox mappings.

Active mailbox: deliver into the provisioned mailbox.
In-Place Archive: use the user's provisioned archive.
Date cutoff: newer mail in the active mailbox, older mail in the archive.
Size-fill: allocate a budget of migrated content to the active mailbox, with older overflow in the archive.

Plan the placement.

Reconstruct supported source folders, optionally inside a wrapper folder. Inspect recorded destination placements alongside export outcomes.

Destination users, licences, mailbox stores and archives must already be provisioned. Source metadata, quotas and the selected write provider affect the route.

Portable mailbox packages

A manageable file handover.

Produce PST batches with configurable naming and file sizing. Keep file generation and upload status separate, then make completed outputs available for authorised download.

Use supported source-folder information in the output.
Inspect folder statistics for suitable completed PST batches.
Record file size and SHA-256 fingerprints.
Use eligible filtered PST packaging for large-message exceptions through the beta migration agent.

Know what the file record proves.

A generated file's fingerprint identifies that artifact. It is not, by itself, verification that a remote system received it.

PST delivery through the agent's SFTP workflow has its own delivery status and size checks. It is separate from the verified EML batch handover below.

Tracked archive ingestion

Follow the batch beyond upload.

Prepare compressed email batches and manifests, stage them in the configured S3 bucket and submit them to Proofpoint ingestion.

Configure the import job, credentials, bucket and region.
Track batch counts, bytes, hashes and external job references.
Distinguish uploaded, submitted and ingestion states.
Download the destination-specific Proofpoint batch report.

Upload is one step.

A file arriving in S3 does not mean Proofpoint has finished ingesting it. Use the recorded batch and ingestion information when assessing completion.

A deployment-level submission hold can separate upload staging from release to ingestion. Its scope is broader than pausing one migration.

Specialist tenant-to-tenant migration

Move between Mimecast tenants.

Transfer archived email into a destination Mimecast tenant through a specialist migration workflow. Message content and mailbox folder metadata are handled as distinct phases.

Collect source content into Simply Discover before sending eligible email to the destination tenant.
Transfer supported mailbox folder and message-location metadata.
Control progression from collection to destination sending through configured approval gates.
Keep invalid-folder outcomes visible for investigation, with progress retained through supported recovery.

Plan the tenant-to-tenant route.

Confirm source and destination access, folder requirements and the deployment procedure as part of a qualified migration engagement.

This route requires specialist setup rather than the standard migration wizard alone. The confirmed scope is Mimecast-to-Mimecast; other source-to-Mimecast combinations need separate confirmation.

Individual messages & customer storage

Content your own process can consume.

Export user-organised message files, with Inbox and Sent Items grouping. EML messages retain their format; raw MSG content keeps its MSG extension.

Make supported message-file outputs available from configured storage.
Add a validated filesystem or SFTP delivery profile for the verified EML batch route.
Publish verified batches with manifests and a ready-for-handover record.

Agree the file layout first.

Raw message export is not a mirror of every source folder. Review naming for multi-domain estates, particularly where addresses share the same mailbox name.

The SHA-256 custody checks described below apply to the supported EML batch delivery route, not every file export or SFTP transfer.

Collect now. Plan the next step.

Source access and target readiness can be separate.

Collect and retain content in Simply Discover without configuring an external export destination at creation.

Start the source collection while destination planning continues.
Inspect the stored content and recorded collection outcomes.
For eligible mailboxes, use the beta migration agent to preview and confirm a later export.
Make retained content available to other enabled, separately licensed platform workflows.

A checked next step.

Later export is subject to source completeness, existing export activity and target-batch eligibility. It is not unrestricted simultaneous delivery to any destination.

Archive search, eDiscovery and DSAR are separate capabilities, not actions that run automatically as part of migration.

Source and destination coverage are qualified separately. The lists on this page are not a promise that every source, item type and target combination is interchangeable.

Changing domains as well?

Use individual mailbox mappings, domain substitution and reviewed defaults for supported Microsoft 365 routes. Map the historical addresses to the intended destination identities before export.

Considering FastTransfer?

FastTransfer is a separate Microsoft destination route. Advanced folder and archive behaviour requires target-tenant validation and provisioning; it should not be assumed to have identical placement options to the M365 Mailbox route.

02 / Define the collection

The right mailboxes.
A boundary you can review.

Select the people, domains and dates that belong in the move. Reuse and test connection configurations, review the plan, then stage work for an agreed start.

A small pilot or a wider estate.

Discover supported mailbox populations, select individual addresses or supply a reviewed list. For Mimecast, eligible metadata-only estimates help assess the scope without first downloading all message content.

For selected Mimecast domains, progressive discovery can admit mailboxes while enumeration continues. Checkpoints and retries preserve productive work if a later discovery step needs attention.

Keep the context the source provides.

Retain available sender, recipient, CC/BCC, message identifiers, dates, attachments and source associations. Supported source-folder information can guide compatible mailbox and PST exports.

Optional Mimecast journal envelopes can carry available original envelope recipients, including BCC information absent from the visible message headers. They cannot recover information the source does not provide.

Supported source paths

Mimecast: Archive collection, mailbox/domain scoping, dates and supported folder information.
Microsoft 365: Mailbox collection with discovery or supplied addresses, date scope and supported item-class selection.
ArchiveManager: Mailbox collection through a reachable, configured proxy.
Gmail: Configured service-account collection. Mailbox scope requires a reviewed setup rather than automatic wizard discovery.
Enterprise Vault: Specialist collection through the platform's connector and proxy configuration.
PST, EML & MSG: Separate supported file-intake workflows, rather than mailbox discovery.

Make attachment policy explicit.

Optional Mimecast attachment rules can select MIME types, extensions or sizes. Removed attachments receive a visible placeholder. Recognised referenced inline images are protected; recognised signed or encrypted S/MIME content skips stripping. Policy changes do not rewrite content already collected.

More than email in the wider platform.

Separate platform connectors support collection from Teams, SharePoint, OneDrive, Slack and supported Zoom content. That is evidence collection, not a promise to rebuild those applications in a new tenant. Qualify the content types and intended output for each project.

03 / Keep the move understandable

An overall number is useful.
The detail makes it actionable.

The Migration Command Centre brings project status, mailbox and domain detail, measured throughput and exceptions together. See what has been discovered, what is stored and what has reached a destination stage.

Discovery & collection

Distinguish source estimates from found items, newly collected content and already-present content. Source mailbox occurrences and unique stored messages are different counts.

Export & acceptance

Follow destination-finished, skipped, failed, queued and processing work. Use the target's relevant acceptance or handover evidence, not the mere existence of an export record.

Pace & capacity

Watch actual items and bytes over time. Interpret throughput and estimates alongside source throttling, destination limits, message sizes and configured worker capacity.

Reconciliation, not just a percentageIllustrative mailbox

1,000source items found

Finished: 930
Skipped: 25
Failed: 15
Queued: 30

These fictional counts add up, but the mailbox is not fully delivered. Skipped reasons, failed items and outstanding work still need a decision. Real reports also distinguish missing content and items without an export status.

Keep successful work moving.

Durable progress and checkpoints support resumable collection. Configured concurrency, project priorities and export windows govern the workload. Eligible completed mailboxes can progress to export while others are still collecting.

Pause and resume operate at defined processing boundaries. Export windows use the runtime's agreed timezone. Stopping closes a migration; it is not a temporary pause.

Give exceptions a route forward.

Group failures by cause, inspect source and target detail, and download exception CSVs. Retry eligible failed work at the appropriate stage instead of treating the whole project as one failed operation.

Oversized or rejected messages stay visible. Where eligible, filtered PST packaging through the beta agent offers an alternative handoff for larger items.

“Can you check this one message?”

Authorised operators can search within a migration, preview stored email and attachments, and inspect recorded source folders and export placements. Controlled EML repair can preserve the original stored record while creating a traceable repaired copy for a supported destination.

Recorded folder placements are supporting evidence. A missing placement row alone does not prove a failed delivery, and repair is not a guarantee that every damaged message can be recovered.

04 / Make the handover specific

Not just “the files are there.”
A verified point of handover.

For the supported EML customer-storage delivery route, Simply Discover goes beyond copying files. A validated filesystem or SFTP destination receives batches with read-back verification and a published custody record.

01
Stage & compare.
Copy to a temporary destination, then read it back. Compare size and SHA-256 with the source artifact before finalising.
02
Verify the final file.
Read back the final file and record source and destination sizes, hashes and verification time. An existing mismatch is an exception, not an instruction to overwrite unrelated content.
03
Publish the batch.
When every planned file is verified, publish and verify the manifest. A .ready marker records the manifest hash and handover time for the customer's downstream process.

A delivery queue with its own controls.

Monitor customer delivery separately from export. Space reserves can pause low-capacity destinations, and operators can pause, resume or retry delivery. A file already in progress may finish its verification before the pause takes effect.

An explicit end to the custody record.

The published handover records what was verified at that point. It does not continuously track files after the customer moves them. Completion with exceptions also reflects relevant source and export exceptions, not just successful copies.

These checks belong to this EML batch route. PST fingerprints, Proofpoint batch records and the agent's packaged-file SFTP transfers provide different forms of evidence.

A record people can work with

The update.
The exceptions.
The sign-off discussion.

Generate the main reports in the background, then share an understandable account of inventory, outcomes and outstanding work.

Migration Progress HTML: Mailbox progress, found items, outcome buckets, skipped reasons and reconciliation.
Migration Summary HTML: Case inventory, unique-message counts, mailbox errors and detailed failed items.
Exceptions & metrics CSV: Source or destination failures and operational figures for follow-up.
Destination evidence Route-specific: Proofpoint batch CSVs; recorded folder-placement CSVs through the reporting API; JSON custody summaries and published manifests for verified storage delivery.

A separate report service supports structured, HTML and PDF migration reports. Not every report has every format. Interpret successful completion using finished outcomes and the actual destination's evidence.

Your environment. Defined responsibilities.

Control where it runs.
Control who can act.

Simply Discover supports customer-hosted deployment in Azure, AWS or on premises. Plan the source access, destination connectivity, storage and enabled migration capabilities around your environment.

Project-scoped access

Migration Admin, Analyst and ReadOnly roles distinguish viewing from privileged operations. Sensitive actions also check access to the relevant migration project or mailbox.

Traceable operations

Material operations such as creation, export starts, policy changes, retries, repair and delivery publication produce audit events. Connection configurations support controlled credential reuse.

Distributed oversight

Configured remote deployments can contribute periodically refreshed migration snapshots, including sync status. Specialist Mimecast remote collection can reconcile uploaded packages using manifests and content hashes.

Migration agent Beta

Ask about the work.
Act within its boundaries.

“Which mailboxes still have issues?” “What was skipped?” The beta migration agent answers recognised questions using the selected migration's recorded state.

Authorised operators can request selected retries, eligible PST exports, later target exports and target-file SFTP delivery. Export launch uses an eligibility preview and matching confirmation; SFTP has its own selection and confirmation checks.

The beta agent supports Mimecast and Microsoft 365 mailbox sources. Available actions depend on role, configuration and eligibility; it is not an autonomous planner for every connector.

The content can support what comes next.

Retained data can support separately enabled eDiscovery investigations and DSAR response workflows. Those capabilities have their own licensing, permissions and controls; they do not run automatically with a migration.

Email archive migration, explained

Practical questions.
Clear answers.

What does Simply Discover Migration do?

It collects historical email from supported sources, delivers it to a configured destination or retains it within Simply Discover, and records progress and exceptions. IT teams can scope mailboxes and dates, review mappings, control execution, inspect individual items and generate reports for project handover.

Can we migrate Mimecast email into Microsoft 365 archives?

Yes, through the supported Mimecast collection and Microsoft 365 Mailbox delivery route. Eligible email can be placed into provisioned active mailboxes or In-Place Archives, with date-cutoff or size-fill placement options. Validate source permissions, mailbox mappings, destination provisioning, quotas and available folder information for the project.

Can we migrate archived email into Mimecast?

Yes. Simply Discover supports a specialist Mimecast-to-Mimecast workflow, with separate message-content and mailbox folder-metadata phases. It requires a qualified migration engagement and the appropriate source, destination and deployment setup. Other source-to-Mimecast combinations need separate confirmation.

Can we collect before the destination is ready?

Yes. A migration can collect and retain content without an external target at creation. For eligible mailboxes, the beta migration agent can preview and confirm a later export. That next step checks source completeness, existing exports and active batches; it is not unrestricted multi-target delivery.

Will folders, attachments and BCC information be preserved?

Preservation depends on what the source provides and what the destination supports. Available message metadata and attachments are collected; optional Mimecast journal envelopes can preserve available envelope recipients. Compatible M365 and PST exports use supported folder information. Raw message export groups Inbox and Sent Items rather than mirroring every folder. Optional Mimecast attachment-removal policies must be agreed explicitly.

Does migration require downtime?

Collection, export and cutover can be planned as separate activities. Held starts, export windows and scoped pause/resume controls help coordinate the work. Whether the source remains accessible, how final changes are captured and when users switch depend on the source, target and project plan. This is not a universal zero-downtime guarantee.

How long will our email archive migration take?

Duration depends on source access and throttling, message sizes, mailbox scope, destination limits, network conditions and configured processing capacity. Use eligible source estimates, a representative pilot and measured throughput to plan. A source-collection ETA is not a promise of final destination completion.

What happens to failed, skipped or oversized messages?

The migration records separate outcome states and exception reasons. Authorised operators can inspect items and retry eligible work. Large or rejected messages can receive targeted handling; eligible size-filtered PST packaging is available through the beta agent. An exception remains visible rather than being counted as a successful delivery.

Is every destination verified with SHA-256 read-back checks?

No. Source, staged and final file SHA-256 checks with published custody manifests apply to the supported EML customer-storage delivery route. PST artifact fingerprints, Proofpoint batch information and other delivery records have different meanings. Verification ends at the recorded handover boundary, not at every subsequent customer action.

Can Microsoft 365 calendar or contact items migrate too?

Microsoft source collection can use supported item-class scope beyond email. That does not establish native calendar, contact or other Exchange-object fidelity for every output. Agree the required item classes and qualify the specific source-to-destination route before the move.

Are exported files automatically encrypted or password-protected?

No. The platform can read supported encrypted stored content where the required metadata is available, but that does not make generated PST, EML or MSG files automatically encrypted or password-protected. Plan output storage, transport security, access and any additional protection for the chosen handover.

Does deleting a migration delete the collected email?

No. Migration deletion removes case-owned migration data through a background process while retaining the underlying email entities and stored message objects. Stopping closes the migration without deleting it. Content retention and deletion need their own agreed lifecycle policy.

Simply Discover Migration

A clear route out.
A considered way forward.

Start with the source, the next destination and the evidence your team needs to accept the move.

Discuss your migration