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 and Google Workspace): 25 MB per message, all attachments together. Larger files are offered as a Google Drive link.
  • Outlook.com (personal): 25 MB per message. Larger files are offered as a OneDrive link.
  • Microsoft 365 work accounts (Exchange Online): 35 MB by default, which an administrator can raise to 150 MB. The Outlook desktop app also has its own 20 MB limit for some account types.
  • Yahoo Mail: 25 MB per message.
  • Proton Mail: 25 MB per message.
  • iCloud Mail: 20 MB per message; Mail Drop sends larger files, up to 5 GB, as a download link.
  • AOL Mail: 25 MB per message.

There's a catch in all of these numbers: the limit applies to the message as it travels, not to the file on your disk. Email carries attachments as text (base64 encoding), which turns every 3 bytes into 4, so a file grows by about a third on the way out. A 20 MB video becomes about 27 MB and goes over a 25 MB limit; in practice, about 18 MB is the most you can attach.

The receiving side has a say too. Gmail accepts incoming messages up to 50 MB, but many company mail servers refuse anything above 10-25 MB, whatever the sender's provider allowed, and the message bounces back to you.

#The Drive / OneDrive fallback: what actually happens

Gmail's fallback: attach a file that's too big and Gmail uploads it to your Google Drive and puts a Drive link in the message instead. When you send, it checks whether the recipients can open the file and offers to share it with them. The recipient sees a Drive card with a thumbnail; opening it plays the video in Drive's viewer.

Outlook.com works the same way with OneDrive: the file is uploaded to your OneDrive, the message carries a link card, and the recipient opens the video in OneDrive's viewer.

iCloud Mail Drop uploads the file to iCloud for 30 days. The recipient gets a download link that works without an Apple account.

#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

Aim for 18 MB of file, to leave room for the encoding. Then the maths is: megabytes x 8,000 / seconds = total kbps, minus about 128 kbps for the audio. A 30-second clip gets about 4,700 kbps for the video - comfortable 1080p. A 2-minute clip gets about 1,070 kbps - 720p. A 5-minute clip gets about 350 kbps - 480p at best, and only for slow content like a shared screen. Longer than that, use the Drive or OneDrive link.

Wave's email page is preset to 18 MB and does this sum for you, in your browser: it picks the bitrate from the clip's length, lowers the resolution when it has to, and writes an H.264 MP4 that plays in any mail app.

#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 needs the Drive or OneDrive link. For an emailable excerpt, trim to the 30 seconds to 2 minutes that matter - Wave's email page trims and compresses in the same pass.

#The takeaway

Gmail and Outlook.com allow 25 MB per message, and Microsoft 365 work accounts can go up to 150 MB. Because attachments grow by about a third on the way out, aim for 18 MB of video. The automatic Drive and OneDrive links handle anything bigger; they work fine for casual video but add friction for recipients in locked-down companies. Compressing to 18 MB is realistic for clips up to about 2 minutes at 720p; for longer meetings and full recordings, send the link.