The exact steps
- Decode each photo
- Limit the longest side to 1600 px
- Encode a compatible JPG at 72% quality
One smaller JPG per source; download the whole batch as a ZIP.
Why this chain
Most email recipients can open JPG, and resizing large camera files saves substantially more bytes than quality adjustment alone.
Honest limits
The exact file size is not guaranteed. JPG removes transparency and is lossy; keep the originals, and check one attachment at full size before sending.