The limits — and why they're smaller than they look
Every mail provider caps a message's total size. The usual magnitudes:
| Provider | Usual limit per mail |
|---|---|
| Gmail | ~25 MB send |
| Outlook.com | ~20 MB |
| Yahoo / others | ~20 MB |
| Corporate mail servers | often only 10 MB — sometimes less |
Two pitfalls hide in these numbers. First, the smaller limit of the two sides counts: your 24 MB mail leaves Gmail without trouble and then fails at the recipient's 10 MB corporate server — as an undeliverable notice minutes later. Second, the encoding surcharge: attachments travel in emails Base64-encoded, and that makes them about a third larger (why exactly is explained in Base64 explained). Rule of thumb from that: attachments together at most ⅔ of the limit — so at a 20 MB limit at most 13 MB of files, for an unknown recipient better under 7 MB.
The way that almost always works: shrink instead of juggle
Smartphone photos are 4–8 MB because they're meant to be enough for poster print. For viewing on screen — which happens with emailed photos in 95% of cases — a fraction is enough:
- Shrink to 2048 px: all photos together into the resize tool (batch works, runs browser-local), long edge 2048 px.
- Save as JPG at quality 80 — if needed, through the compression tool. Result: 300–600 KB per photo.
- Attach and send. Twenty photos in one mail instead of two photos in ten mails.
The quality loss on screen: imperceptible. Only if the recipient wants to print do other numbers apply — see the FAQ below.
The ZIP misconception
The most-attempted wrong way: packing photos into a ZIP archive. The result reliably disappoints, because JPGs are already compressed — ZIP finds hardly any redundancy in them and saves single-digit percentages. What ZIP is good for anyway: bundling many files into one attachment the recipient can save with one click. It solves no size problem.
When the cloud link wins
Above about 20 shrunk photos — or when originals at full resolution are wanted — the attachment is the wrong tool. Then: share a folder in iCloud, Google Drive, Dropbox, or your own provider and mail the link. Gmail and Outlook offer this automatically anyway when the limit is exceeded. Two things to consider: the link should if possible be shared with an expiry date or only for specific recipients — and a link is a hand-over like any other; for sensitive images the same care applies as with an attachment.
Three special cases from practice
- Job application: here the portals' limits apply, not the mail providers' — and an 8 MB attachment looks clumsy in any case. Getting certificate scans small: Shrinking a scan for upload.
- Many scans/pages: don't attach as 14 separate images, but bundle as one PDF — here's how with built-in tools.
- iPhone users: when sharing by mail, iOS directly offers "Small/Medium/Large/Actual Size" — "Large" roughly corresponds to the 2048-px route and is the right choice for most purposes.
A privacy sentence to close
Unlike the big social media platforms, email removes no metadata: GPS position and capture data travel in the attachment. For photos to strangers — a sale, an authority, a forum — run it once through the metadata editor first.
Frequently asked questions
Why does my email with photos come back as undeliverable?
Almost always because of the size limit — and often the recipient's limit, not yours. Your mail goes out, the other side's server rejects it. On top of that: attachments are re-encoded for sending and get about a third larger. 18 MB of photos can thus make a 24 MB mail that fails at a 20 MB limit.
Does zipping photos before emailing help?
Practically nothing. JPG photos are already compressed — a ZIP archive makes them only a few percent smaller, sometimes even larger. ZIP is worth it for bundling many files into one attachment, not for shrinking. Photos only really get smaller by reducing the pixel dimensions or stronger JPG compression.
How many photos fit in a 10 MB mail?
At original size from a smartphone (4 to 8 MB per photo): one to two. Shrunk to 2048 pixels and saved at quality 80 (300 to 600 KB per photo): fifteen to twenty-five. So shrinking makes the difference between 'one mail' and 'eight mails'.
The recipient wants to print the photos — can I still shrink them?
Then better not below 2500 to 3000 pixels on the long edge — that's enough for prints up to about 20 × 30 cm. For larger prints, send the originals via a cloud link. For screen viewing only, 1600 to 2048 pixels is always enough.
Sources
Google — Attachment limits in Gmail · Microsoft — Outlook support · RFC 2045 — MIME (Base64 encoding).