You can resize large blocks of photos to any percentage you choose.
https://www.irfanview.com/
Install the program, open it, then click on File in the upper left, choose "Batch conversion/rename". Once there, place a CHECK mark in the "Use advanced options for bulk resize", then click on the "Advanced" button. Once there, change the "Set new size to percentage of original", and make it 50%, or what ever you choose. (I frequently use 80% and it greatly reduces the file size.) Then add the file to be reduced in the "Batch Conversion" window and go through the steps to reduce their size.
Once that's done, you can find the reduce files in the location you placed them and email more files than before.
Hope this helps.
Grif