Sending Large Attachments via Drive

Most email systems quietly reject attachments larger than about 25 MB. Some get stricter, corporate Outlook deployments often cut you off at 10 MB. The result: you attach a 30 MB PDF, click Send, and 20 minutes later get a delivery failure from a server you've never heard of.

When Drive is available for your mailbox, TrekMail webmail can route large attachments through Drive. The recipient receives a download link instead of a traditional attachment that may bounce. They do not need a TrekMail account to download a valid link.

How auto-routing works

Compose a message in webmail and attach files however you normally do, paperclip button, drag-and-drop into the composer, paste an image from your clipboard. Webmail measures each file as it's added.

If a file is 18 MB or smaller, it stays an attachment. The recipient sees a paperclip icon and downloads the file inline through their email client.

If a file is larger than 18 MB, webmail uploads it to Drive in the background and replaces the attachment with a public download link. The composer shows the file as a link attachment, with its filename and upload progress.

The 18 MB threshold matches what most email systems will reliably accept. Going higher risks bounces from strict recipients; going lower would route too many normal-sized attachments through Drive unnecessarily.

What the recipient sees

The email keeps the subject, body, and signature you wrote. It also includes a Drive-link section with:

• The filename
• The file size
• A download link

Opening a valid link starts the download in the recipient's browser. No login or acceptance step is required.

The message includes both HTML and plain-text link content, so recipients can use it in standard email clients.

Where the file ends up in Drive

Auto-routed attachments are saved in the sending mailbox's Drive space. They do not need to be uploaded a second time to be sent.

If the mailbox has full Drive access, you can find and manage these files from Drive like other files. A mailbox configured for attachment-only Drive access does not have the personal Drive file browser.

These files still count against your storage pool like any other file. If you send dozens of large attachments and never clean up, they accumulate.

Download caps

Each auto-created link defaults to a 100-download cap. After 100 successful downloads, the link stops working, the recipient (or anyone they forwarded it to) sees the "no longer available" page.

100 is generous for normal use. A typical email has one recipient who downloads once. Even with three or four forwards and a couple of recipients on each, you're looking at a dozen downloads. 100 leaves headroom but caps the damage if a link leaks.

The composer-created link uses the standard 100-download cap. For an attachment-only mailbox, the link is also given the mailbox's attachment-retention deadline. To choose a different expiry or download cap, create a public share link for a file in Drive and paste that link into your message.

Sending a file already in Drive

You can also send a file that's already in your Drive without uploading it again. In the composer toolbar, click the Drive icon. A folder picker opens, navigate, pick the file, and a public download link is added to the message. The file isn't re-uploaded; the link points at the existing copy.

This is the right approach for files you keep on hand and send regularly: templates, standard agreements, brand assets, and deliverables you've already prepared. The recipient gets the same Drive-link section, with the standard 100-download cap.

What to do when you don't want auto-routing

Sometimes you want a file to be a real attachment regardless of size, maybe the recipient explicitly asked for it as an attachment, or maybe you're sending to a system that requires inline attachments.

For files 18 MB or smaller, auto-routing doesn't apply, so you're already there.

For files larger than 18 MB, your options are:

• Compress to 18 MB or smaller if possible. ZIP archives, smaller image dimensions, lower-bitrate video.
• Split into multiple files of 18 MB or less and attach them all.
• Send the file via a different channel that supports the size (Drive's public share links work even outside the composer; you can also drop in Slack, SFTP, etc.).

There is no per-message override that forces a large file to be a real attachment, most email systems would reject it anyway.

Pool implications

Auto-routed attachments use storage in your pool. A 30 MB attachment uses 30 MB until you delete it from Drive. The recipient downloading the file does not duplicate the storage.

If you send a lot of large attachments, the pool fills up over time. The fix is the same as any other Drive consumer: delete what you don't need, empty Trash, or expand the pool.

You can also set a habit: regularly review files you created for email and delete anything you no longer need.

Behaviour outside webmail

This automatic option applies only in the TrekMail webmail composer. If you send from Outlook, Apple Mail, Thunderbird, or another email app, that app creates and sends the attachment itself. Use a Drive share link for large files when needed.

In that case:

• Attachments are real MIME attachments, regardless of size.
• Your mail app and the recipient's email system each enforce their own message-size policies.

If you regularly send large files from a desktop email client, the cleanest workflow is: upload to Drive first, generate a public share link, paste the link into your message body. Same recipient experience as the webmail auto-routing, just done by hand.

Common scenarios

"My recipient says they can't download the file." Check the file and its link in Drive. Common causes are an expired link, a download cap that was reached, or a file that was moved to Trash. Moving a file to Trash revokes its active links, so create a new link after you restore the file.

"The file appears as an attachment in some clients but a link in others." That doesn't happen, the message body contains a link in HTML and a textual reference in the plain-text part. Both clients see the link, just in different visual styles. There's no client-specific switching.

"I want to send the same large file to 50 people without 50 different links." Send a single message with the file attached; all 50 recipients see the same link. Or, use a share link and paste it manually into one message you BCC to 50 people.

"My recipient's company strips download links from emails." Some corporate filtering systems treat any external link as suspicious. Workaround: shrink the file or send via a different channel. There's no setting in TrekMail to bypass recipient-side filtering.

What's next

• Public Share Links, the underlying link mechanism, including manual creation and full options.
• Uploading Files to Drive, preload Drive with templates and brand assets so the Drive picker is ready when you compose.
• Pooled Storage Quotas Explained, how attachments factor into your pool.