ChainMail
The PST problem
If you've used Microsoft Outlook for any length of time, you know the PST file. It's the local archive where Outlook stores every email, attachment, calendar entry, and contact. Over months and years, these files grow — 10 GB, 20 GB, 50 GB or more.
And with that growth comes a list of problems that every IT admin and power user has dealt with:
- Performance degradation — as PST files grow past 10–20 GB, Outlook slows to a crawl. Searching takes minutes. Opening the app takes forever. Everything lags.
- Corruption risk — large PST files are fragile. A bad shutdown, a full disk, or a Windows update can corrupt years of email. Microsoft's repair tool (scanpst.exe) doesn't always recover everything.
- Disk space — a 50 GB PST file on a 256 GB SSD means email alone takes up 20% of your storage. Laptops with smaller drives feel it first.
- Backup complications — PST files are locked while Outlook is running, making them difficult to back up reliably. They're too large for most cloud sync tools to handle gracefully.
- Migration headaches — moving to a new PC means copying multi-gigabyte PST files. Moving to a new email provider means importing those files — a process that can take hours and often loses folder structure.
- No real-time sync — if you archive email to a local PST, it's only on that machine. Access it from another device? Not possible without copying the file.
The average enterprise Outlook user accumulates 2–5 GB of PST data per year. After a decade, that's a 30–50 GB file sitting on a laptop SSD.
How ChainMail eliminates this entirely
ChainMail takes a fundamentally different approach. Instead of downloading your entire mailbox to a local file, it streams email from Gmail's cloud via the Gmail API.
Your mailbox lives on Google's servers
All your email — every message, every attachment, every label — stays in Gmail. Google manages the storage, the backups, and the redundancy. You get 15 GB free (or more with Google Workspace plans), and it's accessible from any device, any browser, or any app that connects to the Gmail API.
Local cache, not local archive
ChainMail maintains a lightweight local cache of recent messages for fast access and offline reading. This cache is measured in megabytes, not gigabytes. It's automatically managed — old cache entries are cleaned up, and the app never asks you to "compact" or "archive" anything.
Attachments on demand
Attachments are downloaded when you open an email, not stored permanently in a growing archive. They're cached locally for quick re-access, but the cache is bounded and managed automatically. No more 200 MB PowerPoint files permanently bloating your local storage.
No corruption, no repair tools
Because there's no monolithic archive file, there's nothing to corrupt. If your local cache ever gets into a bad state, ChainMail simply rebuilds it from Gmail. Your email is always safe on Google's servers.
| Aspect | Outlook + PST/OST | ChainMail + Gmail |
|---|---|---|
| Local storage used | 10–50+ GB (grows forever) | ~100–500 MB (managed cache) |
| Corruption risk | High (especially >20 GB) | None (cache is rebuildable) |
| Search speed on large mailbox | Degrades with size | Constant (Gmail server-side search) |
| New PC migration | Copy multi-GB files | Sign in, cache rebuilds automatically |
| Backup strategy | Manual PST backup needed | Gmail handles it (Google infrastructure) |
| Multi-device access | PST is single-machine | Sign in anywhere, same mailbox |
| Archive management | Manual compaction, AutoArchive | None needed |
Who benefits most
- Long-tenure employees with 10+ years of email accumulated in Outlook — the biggest PST headaches
- Laptop users where SSD space is limited and a 50 GB PST is a real problem
- IT admins tired of fielding "Outlook is slow" tickets that always trace back to oversized PST files
- Organizations migrating to Google Workspace who want to leave PST files behind entirely
- Anyone who's ever lost email to PST corruption and never wants to deal with scanpst.exe again
Frequently Asked Questions
Can I import my existing PST files into ChainMail?
ChainMail connects to Gmail, so the right approach is to import your PST into Gmail first (using Google's migration tools or a third-party importer), then access everything through ChainMail. Once it's in Gmail, ChainMail sees it immediately.
How much disk space does ChainMail use?
The app itself is about 150 MB. The local cache grows as you use it but stays in the hundreds of megabytes range — orders of magnitude smaller than a typical PST file. Attachments are cached on demand and cleaned up automatically.
What if I need offline access to old emails?
ChainMail caches recently viewed messages for offline access. For deep archive searches, you'll need an internet connection so ChainMail can query Gmail's servers. In practice, this is the same as how Gmail works in a browser.
Is my email still safe if my computer dies?
Yes. Your email lives on Gmail's servers. If your computer dies, buy a new one, install ChainMail, sign in, and everything is there. No file recovery, no backup restoration.
What about Gmail's storage limits?
Free Gmail accounts get 15 GB shared across Gmail, Drive, and Photos. Google Workspace plans offer 30 GB to unlimited storage depending on the tier. ChainMail doesn't add to or change your Gmail storage usage.