Do Photos Lose Their Metadata When Emailed?
Email itself keeps the file intact. The apps at either end often do not.
An email attachment is sent byte for byte, so the metadata survives the journey. Save the attachment and the date inside is usually still there.
The apps around it are the problem. Phone mail apps often resize photos to save data, and a resized photo is a new file with most of its metadata gone. Web mail clients sometimes do the same.
If you are collecting family photos by email, ask for the originals, and check one before you ask for a hundred. Takeout JSON Metadata Fixer can repair what did survive. It runs on your own computer and is free for your first 500 photos.