Never Hit the Outlook
50 GB Limit Again.
Automated, cloud-native attachment stubbing for Exchange Online. Shrink mailbox size by up to 80–90%, fix slow desktop Outlook performance, and avoid expensive tier plan upgrades.
The Desktop Outlook Reality
Over 80–90% of SMB employees rely heavily on Classic Desktop Outlook for keyboard shortcuts, document management, and multi-mailbox workflows. But local .ost cache database files break down near 50 GB.
The 50 GB Ceiling & OST Bloat
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Mailbox Full Bounce: Mailbox hits 50 GB → Microsoft blocks all incoming & outgoing mail delivery
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Desktop Outlook Freezes: Local
.ostbinary database grows to 40+ GB → severe disk I/O thrashing & frequent "Not Responding" lockups -
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Search Indexer Spikes: Windows Search constantly grinds re-indexing 40 GB of inline binary attachments → CPU spikes & battery drain
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Forced Upgrades: To get higher native storage caps without archiving friction, Microsoft pushes expensive plan upgrades to E3 ($23/user/mo)
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For 25 Users: Upgrading plans to reach higher caps costs up to $6,900/year extra — just for email storage
The Mailarch Solution
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100% Cloud-Native: Background worker scans mailboxes via Microsoft Graph API — zero desktop agents
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Smart Offloading: Extracts heavy attachments (>250 KB) from emails older than your chosen threshold
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1-Click Secure Links: Replaces attachments with clean download links right inside the original email body
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Lean .ost Cache: Local database shrinks from 50 GB down to ~8 GB → Outlook launches instantly
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Full Search Intact: Attachment text content is preserved so Outlook search still finds keywords instantly
Why Microsoft's Native Archiving Fails Users
Enabling Microsoft's native Exchange Online Archiving solves storage capacity on paper, but creates painful day-to-day user friction.
Parallel Folder Hierarchy
Native archiving moves old emails into a completely separate, cloned folder tree (In-Place Archive - User). Employees are forced to manage two identical sets of folders (Inbox vs Archive\Inbox, Sent vs Archive\Sent), leading to confusion and lost emails.
No Offline Access
Microsoft's online archive is strictly cloud-only. When employees travel, work on airplanes, or experience Wi-Fi drops, they lose access to their archived emails entirely — unable to read even basic email body text or subject lines.
Broken & Truncated Search
Desktop Outlook instant search prioritizes the local .ost cache. Searching archived items forces a slow "Search on Exchange Server" query that often times out, truncates search results, or fails when offline.
💡 The Mailarch Difference
Mailarch keeps all email body text, headers, and conversation threads in your primary Inbox, preserving full offline reading and instant search. Only the heavy binary attachments are offloaded to cheap cloud storage and accessed via 1-click links.
Up and Running in 3 Steps
No software installs. No agent deployments. No PowerShell scripts. Just one OAuth click and you're live.
Connect Your M365 Tenant
Your IT admin clicks "Sign in with Microsoft" and grants access via standard Entra ID admin consent. Takes 60 seconds. Zero portal navigation required.
See Your Savings Instantly
Mailarch scans mailbox metadata and shows a real-time dashboard: "You have 340 GB in offloadable attachments across 18 mailboxes. Offloading avoids 6 license upgrades."
Silent Background Migration
Automated trickle processing runs at 50–100 emails per batch, largest files first. Users see zero Outlook disruption — no sync storms, no Monday morning lag.
Built for the Edge Cases
We've thought through every scenario an IT admin worries about.
Digitally signed emails are automatically detected via multipart/signed content headers and bypassed completely. Cryptographic integrity is never touched.
Company logos and signature graphics (isInline=true, <250 KB) are never detached. Only non-inline files above your size threshold are processed.
During extraction, attachment text content is injected as a hidden HTML block in the email body — so Outlook search still finds keywords inside PDFs and docs.
Pre-flight API check detects active legal holds. Original .eml is preserved in a WORM-locked GCS bucket (SEC 17a-4 compliant) before any modification.
Processes 50–100 emails per batch, oldest & largest first. Desktop Outlook syncs updates silently in the background — no Monday morning sync storms.
Download links work on Outlook Mobile, OWA, and every third-party mail client. Responsive auth portal supports single-click downloads on any device.
How Mailarch Compares
Side-by-side against the alternatives SMBs and MSPs consider.
| Capability | Legacy Desktop Tools | M365 Online Archiving Native M365 |
M365 E3 Upgrade $23/user/mo |
mailarch.io |
|---|---|---|---|---|
| Cloud-native, zero desktop install | ✕ *(Desktop EXE)* | ✓ | ✓ | ✓ |
| Automated background processing | ✕ *(Manual batch)* | ✓ *(MRM Policies)* | ✓ *(MRM Policies)* | ✓ *(Graph API)* |
| Preserves primary folder structure | ✓ | ✕ *(Cloned Archive tree)* | ✕ *(Cloned Archive tree)* | ✓ *(Same Inbox)* |
| Offline reading of email body text | ✓ | ✕ *(Online-only storage)* | ✕ *(Online-only storage)* | ✓ *(Local .ost)* |
| Instant local Outlook search | Partial | ✕ *(Server query required)* | ✕ *(Server query required)* | ✓ *(Text injected)* |
| Multi-tenant MSP management | ✕ | ✓ *(Partner Center)* | ✓ *(Partner Center)* | ✓ *(Dedicated Archiving Hub)* |
| Per-company flat pricing | ✕ *(Per-seat)* | ✕ *(Per-user)* | ✕ *(Per-user)* | ✓ *(From $9/mo)* |