Why email hates big photos
Most email providers cap total attachment size somewhere between 20–25MB per message, and mobile carriers or corporate mail servers often enforce tighter limits than that. A single modern phone photo can already be 5–8MB, so attaching six or seven vacation photos to one email is a common way to hit the wall — and the failure message rarely explains exactly which limit you tripped.
What size actually works reliably
A practical target is 1–2MB per photo for a handful of images, or under 500KB each if you're attaching a dozen or more. Gmail, Outlook, and Yahoo Mail all handle these comfortably, and recipients on slower connections or metered mobile data will thank you — nobody wants to wait on a 6MB photo attachment over cellular.
The two-step fix
Resize before you compress. A photo doesn't need to be 4000 pixels wide to look sharp in an email client, which typically displays images at 600–1000px anyway. Cutting the pixel dimensions down first means the compression step that follows has to discard far less detail per pixel to hit the same file size target — the result looks noticeably better than compressing the full-resolution original down to the same size.
Sending many photos at once
If you're attaching more than 4–5 photos, most email clients will silently compress them anyway when you choose a smaller 'attachment size' setting in the send dialog — but that compression is often aggressive and inconsistent across providers. Compressing each photo yourself to a known size beforehand gives you predictable, consistent quality across every recipient's email client.
When to use a link instead
For a genuinely large batch — twenty, fifty, a hundred photos — attachments stop being the right tool entirely. A shared cloud folder link (Google Drive, Dropbox, iCloud) avoids the size ceiling completely and lets recipients download only what they want, rather than receiving one enormous email.