Set one total size for a whole batch of photos, for example 2 MB for an email, and the tool shares that budget across all of them.
If the set still won’t fit at the lowest quality, the tool scales the photos down as well. Setting a max width yourself first often gives a better-looking result.
Normal tools size each file separately. This one treats the whole batch as a single budget and adjusts every photo together until the total fits.
The tool shrinks quality, then dimensions, and tells you if it still can’t fit so you can raise the budget or remove images.