Sending large file attachment to email?

Mail Drop lets you send large files like videos, presentations, and images through iCloud. If you shared links through Mail Drop that are no longer available, you might have exceeded one or more of the service limits.

With Mail Drop, you can send attachments up to 5 GB in size. You can send these attachments right from Mail on your Mac, the Mail app on your iPhone, iPad, or iPod touch, and from iCloud.com on your Mac or PC. All files types are supported and attachments don’t count against your iCloud storage. If a message, including its attachments, is larger than your Internet Service Provider (ISP) limit, Mail will ask you to send the attachments using Mail Drop.

An article for it : Mail Drop limits - Apple Support

Email is not conducive for sending large attachments. Your ISP as well as the recipient's ISP or email server typically restricts email size. You can use an online cloud service to send large files.