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How to Send CAD Files via Email in 2025: Complete Guide to Large File Sharing

Deqian Jia
Deqian Jia
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CAD FilesEmailFile SharingEngineeringLarge Files

If you are here, it is probably because something very normal just happened:

  • Your STEP or SolidWorks assembly is hundreds of megabytes.
  • Your email client says “attachment too large” or silently fails.
  • A supplier or client is waiting, and you do not want to start playing IT support.

You are not alone. Large CAD assemblies and neutral formats like STEP/IGES routinely end up in the 50 MB – 1.5 GB range, especially for complex parts and assemblies. Most email systems, on the other hand, top out at 20–25 MB per message (Gmail ~25 MB, Outlook.com ~25 MB).

Let's walk through why this is hard, what you actually want instead of "one more attachment," how to do it cleanly with Peony, and what to use if Peony is not available yet.

1. What makes sending large CAD files challenging

CAD files are painful for email for a few structural reasons:

1.1 Size vs email limits

  • Native CAD files (SLDASM, SLDPRT, RVT, DWG, etc.) and neutral formats (STEP, IGES, Parasolid) blow past typical 20–25 MB attachment limits.
  • Even when email allows it, recipients’ servers or security gateways may reject or quarantine big CAD attachments.

1.2 Complex file dependencies

  • Assemblies often reference hundreds of parts and subassemblies plus textures, drawings and configs.
  • Sending “just one file” can break references on the other side unless you pack everything correctly.

1.3 Tool and version mismatch

  • Your customer might be on a different CAD system or a different major version.
  • You often need to send both a neutral format (STEP/IGES) and PDF drawings for people without CAD seats.

1.4 Security and IP

So the problem is not just "file too big." It's size + structure + security + compatibility all colliding.

2. What you really want instead

If we translate your frustration into requirements, you probably want something like this:

  1. Guaranteed delivery, no bounces

    • One link that works whether the file is 30 MB or 3 GB.

  2. A proper “package,” not random loose files

    • Native CAD, neutral STEP, and PDFs bundled in a way that keeps context together.

  3. Control after sending

    • Ability to revoke access, update files (e.g., new revision) and avoid version chaos across ten email threads.

  4. Security that matches the value of the CAD

  5. Low friction for recipients

    • They should not need to create a new account in a niche tool or fight with VPNs.
    • Download CAD if they need to open it; preview PDFs and lighter assets in-browser.

Email is good at sending messages. You want something that is good at handling large, sensitive, structured engineering data and then let email just carry a link.

3. How to send large CAD files using Peony (step by step)

Here is a workflow that tends to work well for hardware, architecture and manufacturing teams.

Step 1 – Prepare a clean CAD package

Before you upload:

  • Use your CAD system’s “Pack and Go” / “ePack” / “eTransmit” equivalent to gather:

    • The assembly
    • All referenced parts/subassemblies
    • Drawings (DWG/PDF)
    • Any required textures or libraries

  • Export a neutral format (STEP or IGES) plus PDFs for people who do not have CAD.

Optionally zip the whole package to keep everything tidy.

Step 2 – Create a dedicated Peony room for that partner/project

In Peony:

  1. Create a room like:

    • “ACME – Gearbox Assembly CAD (Rev B)”
    • “Architect – Structural Model Package”

  2. Upload your CAD package (native files, STEP/IGES, PDFs, ZIPs).

Peony is built to handle large files and keeps them encrypted at rest while providing structured access control and logging through secure document sharing platforms.

Step 3 – Set access and permissions

For external recipients:

  • Add their email addresses (or domain, if appropriate) using identity-bound access.
  • Add passwords to Peony rooms for an additional layer of protection—you can require both identity verification and a password.
  • Decide per role:
    • Engineers / vendors: allow download of CAD and neutral files.
    • Managers / clients: view-only access to PDFs and documentation.

You can:

  • Keep highly sensitive items view-only (for example specification PDFs).
  • Turn on watermarking for drawings or documents so any screenshot includes recipient identity.

Step 4 – Add optional security layers

If the model is particularly sensitive:

  • Enable a passcode on the room or share link using password protection.
  • Share the passcode over a separate channel (SMS, call, Signal) rather than in the same email.
  • Enable screenshot protection for attached documents where relevant (e.g., manufacturing instructions, pricing).

This lines up with common CAD-security recommendations: encrypt in transit and at rest, restrict access, and monitor usage. Peony provides access management and tracking for complete CAD IP protection.

Step 5 – Share a single link via email

Now your email becomes simple:

“Here’s a secure link to the full CAD package (native files, STEP, PDFs). You can download what you need from there; we will keep this link updated with the latest revision.”

If you later fix an interference, change a tolerance or add a missing part:

  • Update the files inside Peony.
  • The same link now points to the latest package; you are not chasing everyone with “please ignore previous version” emails.

If the project ends, you revoke access to the room using access management or just remove the external users. See who accessed CAD files with page-level analytics: when, how long they viewed them, and which parts they engaged with.

4. Other methods if you cannot use Peony

If Peony is not an option yet, you still have reasonable fallbacks.

A) Cloud storage (Drive / OneDrive / Dropbox / CAD-specific clouds)

You can:

  • Upload CAD packages to Google Drive, OneDrive, Dropbox, or CAD-focused platforms (Autodesk cloud, Rakuten Drive, GrabCAD Workbench, Triofox-style solutions).
  • Share links restricted to named users rather than "anyone with the link."

Pros:

  • Handles large files far beyond email limits.
  • Some platforms offer in-browser previews (e.g., DWG in Dropbox).

Cons:

B) Dedicated secure file-transfer services

You can also use secure file sharing tools with end-to-end encryption and password-protected links, as covered in independent reviews of secure file-sharing apps.

Pros:

  • Strong confidentiality and simple “send large file” flows.

Cons:

  • Often geared toward one-off transfers, not ongoing collaboration or structured CAD packages.

C) Old-school: FTP / SFTP

Some partners still expect an FTP/SFTP endpoint:

  • Works fine for very large files.
  • But it is clunky, hard for non-technical users, and usually lacks modern audit and sharing UX.

5. Practical tips to make this painless

A few habits will save you a lot of headaches:

  • Always send a neutral format + PDF So even if your counterpart’s CAD or version is different, they can at least inspect the geometry and drawings.

  • Standardise “one room per client/project” Whether in Peony or another system, give each major client or project a dedicated space for CAD packages. This cuts down on hunting across email threads.

  • Document your revision rules Decide when you update vs create a new room, how you name revisions, and who is allowed to upload CAD vs view only. This is echoed in modern CAD storage best-practice guides.

  • Stop using raw email attachments for big CAD Treat email as a notification channel, not a file transport. The CAD lives elsewhere. Use Peony for secure CAD sharing with identity-bound access, password protection, watermarking, and tracking.

Done right, sending a huge CAD assembly stops feeling like a mini-crisis and starts feeling like a calm, predictable flow: upload once, share a link, stay in control of the package and the IP it represents.

Frequently Asked Questions

How do you send large CAD files via email?

Email attachment limits (20–25 MB) block most CAD files. Peony is best: upload CAD packages to a secure Peony room and share one protected link via email with identity-bound access, password protection, and tracking.

What's the file size limit for sending CAD files via email?

Most email systems limit attachments to 20–25 MB, but CAD files often exceed 50 MB–1.5 GB. Peony has no file size limits—upload CAD packages to a secure Peony room and share one protected link.

How do you securely share CAD files?

Peony is best: upload CAD packages to a secure Peony room with identity-bound access, password protection, watermarking, screenshot protection, and analytics in one platform.

Can you see who accessed shared CAD files?

Most platforms provide limited or no access tracking. Peony provides complete visibility: see who accessed CAD files, when, how long they viewed them, and which parts they engaged with.

What's the best way to share CAD files with clients?

Peony is best: upload CAD packages to a secure Peony room with identity-bound access, password protection, watermarking, and tracking, then share one protected link instead of email attachments.

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