Secure File Sharing for Agencies: A Practical Guide

The Email Attachment Problem

Sending contracts, tax returns, and financial reports as email attachments is convenient — and dangerously insecure. Here's why:

• No access control: Anyone with the recipient's email can open the attachment
• No revocation: Once sent, you can't take it back
• No audit trail: You don't know who opened it or when
• Size limits: Most providers cap attachments at 25MB
• Inbox sprawl: Files get buried in threads and lost

What Secure File Sharing Looks Like

A proper file sharing system should give you:

Granular Permissions

Not every client document needs to be visible to every team member. You should be able to share financial reports with the CFO but not the intern.

Expiring Links

Send a link that works for 7 days, then auto-expires. No stale access floating around.

Download Tracking

Know exactly who downloaded what and when. This matters for compliance in industries like accounting and law.

Encrypted at Rest and in Transit

Files should be encrypted both on the server and during transfer. This means even if someone intercepts the data, they can't read it.

How Centralyn Handles It

Files uploaded through Centralyn are stored in Cloudflare R2 with server-side encryption. When a client downloads a file, we generate a time-limited signed URL. No permanent public links exist.

• Document requests: Ask clients to upload files directly to their portal instead of emailing them
• Folder organization: Create structured folders per project or document type
• Version history: Upload new versions without losing the old ones

Three Rules for Your Team

1. Never email sensitive attachments — send a portal link instead
2. Review shared file permissions monthly — revoke access when projects end
3. Use document request templates — clients upload to you, not the other way around

Secure file sharing isn't complicated. It's just a habit change. And once your team makes the switch, you'll wonder why you ever used email attachments.