What is “message too large”?
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You attach a PDF, a few images, and a spreadsheet, hit send, and your email bounces back with "message too large." That means your email (including all attachments) exceeded the maximum file size the receiving server will accept. It's a hard bounce.
Most servers technically allow up to 25 megabytes. But "allowed" and "safe for deliverability" aren't the same thing. In practice, anything larger than 5-10MB starts causing problems. Large attachments trigger spam filters, slow down mail servers, and sometimes fail silently (the server just drops the email without telling you why).
This is different from Gmail's clipping limit. Gmail clips emails larger than 102 kilobytes, but it clips the display, not the delivery. The email still reaches the inbox. Message too large is a hard failure. The email doesn't arrive at all.
Here's the fix. Compress your images before attaching. Use a tool like TinyPNG or ImageOptim to cut file sizes in half. If your file is still too large, don't attach it. Use cloud storage instead (Google Drive, Dropbox, OneDrive). Include a secure link in the email body. Your recipient gets a faster email, you avoid bounces, and you look more professional.
Want to test your message size? Check it in your email header before sending. If you're regularly hitting size limits, that's worth understanding whether it's your ESP's threshold or the receiving server's. Our SOS team can review your sending setup and help you find the right balance.
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