You attach a few photos, hit send, and the email either bounces or never arrives. Almost every email service limits the total size of attachments, and the limit is smaller than most people expect.
Remember that attachments grow by about a third when email encodes them, so a 10 MB pile of files can count as roughly 13 MB. The recipient's limit matters as much as yours.
Phone photos are huge because they are made for printing. For email and screens you rarely need more than 1600 pixels on the long side.
Ten photos at 400 KB is only 4 MB, comfortably under any limit.
If you are sending scans, receipts or screenshots, merge them into a single PDF with our images to PDF tool. One tidy file is easier for the recipient than twelve loose images.
For truly big files such as videos or design projects, upload to a cloud drive (Google Drive, OneDrive, Dropbox) and share a link. Check the sharing permission so the person can actually open it. "Anyone with the link can view" is usually the simplest.
Zipping groups many files into one and can slightly reduce size. It will not help much with photos or PDFs, which are already compressed, and some corporate filters block zip files, so use it only when you must.
Try fewer files per message, check the recipient's address for typos, or ask them to confirm their limit. For exact size control see how to compress an image to a target size.