Why email rejects large photo attachments
Gmail limits total attachment size to 25 MB per email. Outlook.com uses the same 25 MB cap. Corporate Exchange servers — the kind used by most companies, schools, and government offices — typically enforce tighter limits: 10 MB is common, and some are set to 5 MB. These limits haven't meaningfully increased in over a decade, but iPhone camera resolution has more than doubled.
A photo taken on a recent iPhone can be 8–15 MB in HEIC format, or 5–10 MB as a high-res JPEG. Three holiday photos already exceed what many corporate email servers will accept. The error message — "Message size exceeds maximum permitted" or "Attachment too large" — appears only after you've already waited for the upload, which makes it especially frustrating.
How much does compression reduce photo size?
Converting a HEIC photo to JPG at quality 85 typically produces a file 1.2–2× the size of the original HEIC (JPEG is less efficient than HEIC compression). That alone doesn't help with email limits. But combining format conversion with JPEG quality adjustment brings the size down significantly:
- Quality 85 (default): visually identical, ~30–50% size reduction vs a raw JPEG export
- Quality 70: slight loss, imperceptible at screen size, typically under 2 MB per photo
- Quality 60: visible compression artefacts on close inspection — use for thumbnails only
For most email use — sending photos to family, sharing event pictures, attaching property photos for a real estate agent — quality 80–85 is the right choice. The recipient sees no difference on their screen or phone.
How many photos fit in one email after compression?
A typical iPhone photo compressed to JPG quality 80 comes out at 1–2.5 MB depending on the scene complexity. That means:
- Gmail (25 MB): roughly 10–20 compressed photos per email
- Outlook / Exchange 10 MB: roughly 4–8 compressed photos
- Strict corporate 5 MB limit: 2–4 photos, or use a file-sharing link instead
If you need to send more than 20 photos, compress them all here, download the ZIP, and share via Google Drive, Dropbox, or iCloud link instead of attaching directly.
Converting without uploading your photos
Online compressors that work by uploading to a server introduce two problems: they're slower (you upload, they process, you download), and your photos — including embedded GPS coordinates and timestamps — pass through someone else's infrastructure.
LocalJPG compresses and converts entirely in your browser using WebAssembly. Nothing is transmitted. You can verify this: open Developer Tools (F12), go to the Network tab, then drop a photo onto the converter. The request log stays empty.
Sending iPhone HEIC photos specifically? HEIC to JPG Converter covers why Windows and email clients often can't open HEIC files directly.
Frequently asked questions
What is the attachment size limit for Gmail and Outlook?
Gmail and Outlook.com both limit attachments to 25 MB per email. Corporate Exchange servers often enforce 5–10 MB limits set by IT administrators.
Will compressed photos look worse?
At quality 80–85, no. The difference is imperceptible at screen viewing sizes. The recipient's phone or monitor will display the compressed photo identically to the original.
How many iPhone photos fit in a 25 MB email?
Roughly 10–20 after compression, depending on the scene. A typical iPhone photo compresses to 1–2.5 MB at quality 80.
Is my data uploaded anywhere?
No. All processing happens in your browser. No photos are sent to any server.