Attachment Stubbing,
Reimagined for the Cloud.
No desktop agents. No COM add-ins. No PowerShell scripts. Mailarch runs entirely via the Microsoft Graph API — processing mailboxes in the background while users work undisturbed.
Cloud-to-Cloud Architecture
Attachments flow directly from Exchange Online to encrypted cloud storage via Graph API. No data touches your local machines. No VPN tunnels. No staging servers.
Smart Targeting Rules
Configure policies: "Strip attachments >5 MB from emails older than 2 years." Filter by sender domain, file type, folder, or custom date ranges.
Largest-First Processing
Targets the biggest files first — 200 emails with 20 MB attachments frees 4 GB instantly, while only requiring Outlook to sync 200 tiny text records.
Clean Download Links
Each attachment is replaced with a secure, branded HTML banner inside the email body. One click opens the authenticated download — works on desktop, mobile, and OWA.
Trickle Migration Engine
Processes 50–100 emails per batch to avoid Outlook sync storms. Initial backfill runs over 3–7 days silently in the background — zero user disruption, zero helpdesk tickets.
Real-Time Savings Dashboard
Instant tenant-wide scan via Reports API shows which mailboxes are near quota limits. See GB freed, license upgrades avoided, and monthly cost savings at a glance.
Engineered for Every Edge Case
Enterprise-grade attachment stubbing with none of the legacy pitfalls.
Emails with multipart/signed or PGP content types are automatically detected and completely bypassed. Cryptographic hashes are never invalidated. Your legal and compliance teams can rest easy.
Only non-inline files (isInline == false) above your size threshold (default: 250 KB) are processed. Company logos, email signatures, and embedded screenshots are never touched.
Microsoft indexes text inside PDFs, DOCX, and XLSX natively. During extraction, Mailarch injects the attachment's text content as a hidden HTML block — so Outlook search still finds keywords that existed only inside the file.
Before processing any mailbox, Mailarch runs a pre-flight LitigationHoldEnabled check via Graph API. If active, the admin is alerted. The original .eml is always preserved in a WORM-locked GCS bucket (SEC 17a-4, CFTC compliant).
Batch size capped at 50–100 emails to keep ICS (Incremental Change Synchronization) under the radar. Oldest emails processed first. Users on Monday morning see a tiny delta, not a 20,000-item sync storm.
When a user forwards a stubbed email, the recipient receives the secure download link — identical to how SharePoint/OneDrive links work natively. No broken binary placeholders or dead references.
Download links open a responsive, mobile-friendly auth portal. Single-tap download on iOS/Android Outlook. Works on any mail client that renders HTML — not just Microsoft apps.
After attachments are removed, Outlook reclaims disk space via idle-time automatic compaction (24–48 hours). For immediate shrink, users/admins can run Compact Now from Account Settings.
Why Desktop Outlook Crawls
The real reason 80% of support tickets exist: a 25-year-old database engine.
The .ost Monolith
Desktop Outlook stores all emails, attachments, and calendar items in a single monolithic .ost binary database (Extensible Storage Engine / Jet Blue). Attachments are embedded as inline BLOBs directly inside database pages.
When this file reaches 30–50 GB, page fragmentation skyrockets. Simple reads, folder switches, and cache lookups cause severe disk I/O thrashing — especially on corporate laptops with endpoint security agents (CrowdStrike, Defender for Endpoint) scanning every database page write.
The Mailarch Fix
By replacing binary BLOBs with lightweight text links, the .ost database shrinks from 50 GB to 3–8 GB. The result is dramatic:
- ✓ Outlook startup: 45 seconds → 1–3 seconds
- ✓ Folder switching: "Not Responding" → instant
- ✓ Search speed: minutes → sub-second
- ✓ Sync on roaming/WiFi: massive bandwidth → negligible
- ✓ Local disk space: 50 GB freed per user