Email attachment size limits are older than most other file-sharing constraints on the internet, and email itself hasn't added a native way to send larger files. So every major email provider grew a "when the attachment is too big, upload it to our cloud storage and send a link instead" fallback - Gmail to Google Drive, Outlook to OneDrive, ProtonMail to Proton Drive. The mechanics are similar; the specific caps differ.

#Current attachment size limits

  • Gmail (personal, Google Workspace): 25 MB per outgoing message, summed across all attachments. Larger triggers automatic Drive upload with a share link.
  • Outlook.com (personal / free): 20 MB per attachment. Larger triggers automatic OneDrive upload.
  • Outlook (Microsoft 365 Business): Default 20 MB, admin-configurable up to 150 MB. Some enterprise tenants raise this specifically for external mail.
  • Outlook (Enterprise E5 with Exchange Online): Up to 150 MB per attachment when the admin has raised it.
  • Yahoo Mail: 25 MB per attachment.
  • ProtonMail (free): 25 MB total per message. Paid plans have 100 MB.
  • iCloud Mail: 20 MB per message; larger triggers Mail Drop (Apple's equivalent of Drive fallback).
  • AOL Mail: 25 MB per attachment.

Note that these are attachment-sending limits; the receiving side may enforce lower caps. Gmail refuses incoming attachments above 50 MB (which is the total server-side email envelope limit, roughly 33 MB when accounting for base64 encoding overhead). Corporate mail servers often refuse anything above 10-25 MB regardless of what the sender's provider allowed. So sending a 25 MB attachment via Gmail to a customer whose company caps at 10 MB fails silently on the receiving side.

#The Drive / OneDrive fallback: what actually happens

Gmail's fallback: attach a file above 25 MB and Gmail offers a dialog: "This file is too large to attach directly. Would you like to send as a Google Drive link?" Click Yes and Gmail uploads the file to your Drive (into a folder Gmail creates called "Gmail Attachments"), sets sharing permissions to "anyone with the link", and inserts a Drive-styled attachment card into the message. The recipient sees a preview thumbnail plus a "Open in Drive" button; clicking opens the file in Drive's preview UI. For video, Drive plays inline in the preview pane on most browsers.

Outlook.com's fallback works similarly with OneDrive. Attach a file above 20 MB, get "This file is too large to attach directly. Send as OneDrive link?", upload happens automatically, recipient sees a OneDrive card with preview and open-in-OneDrive button. Sharing permissions default to "anyone with the link" for external mail.

iCloud Mail Drop uploads to Apple's CDN with a 30-day expiration. The recipient sees an inline attachment card; clicking downloads the file directly, no iCloud account required. Files above 5 GB go through the Mail Drop path automatically.

#When the fallback is fine

  • The recipient uses Gmail or Google Workspace and Drive preview is fine for them.
  • The recipient uses Outlook and OneDrive preview is fine.
  • The video is casual - meeting recording for a colleague, personal moment for family - and the extra click doesn't matter.

#When the fallback creates friction

  • The recipient is in a locked-down enterprise that blocks external Google Drive or OneDrive links (security policy, common in finance/health).
  • The recipient uses a mail client that doesn't render the Drive/OneDrive card gracefully - some corporate Outlook installs show a broken preview and require the recipient to click into the message body to find the link.
  • The video is important enough that "download and view separately" reduces the odds of the recipient watching it. Marketing content, sales collateral, product demos - anything you'd rather have play inline in the mail thread.

#Fitting a video inside 25 MB

The math from /compress-video-for-email/: file size in MB x 8192 / duration in seconds gives total kbps; minus 128 kbps audio = video bitrate. A 30-second clip fits comfortably at 1080p (6700 kbps target). A 2-minute clip fits at 720p (1580 kbps target). A 5-minute clip fits at 480p or lower (550 kbps). Longer than that and target-size compression falls apart at watchable quality - use the Drive fallback.

#Video-call recording sizes to plan around

  • Zoom local recording: ~300-500 MB per hour of 720p meeting.
  • Teams cloud recording: ~400-800 MB per hour, downloaded from SharePoint.
  • Google Meet recording: ~250-400 MB per hour, saved to your Drive.
  • iPhone screen recording (1080p): ~200 MB per 5 minutes.
  • Mac screen recording (retina): ~500 MB per 5 minutes.
  • OBS 1080p60 recording: ~100 MB per minute at reasonable bitrates.

A full-length meeting recording essentially always uses the Drive/OneDrive fallback. For an emailable excerpt, trim to the essential 30 seconds - 2 minutes and compress with the tools in the email compression page.

#The takeaway

Gmail caps at 25 MB, Outlook.com at 20 MB, enterprise Outlook up to 150 MB. The automatic Drive/OneDrive fallback handles larger files with a link; it works fine for casual video but can create friction for high-signal content or locked-down recipients. For genuinely emailable video, target-size compression to 25 MB is realistic for clips up to 2 minutes at 720p or 5 minutes at 480p. For longer meetings and full recordings, the Drive fallback is the right tool.