How to send large attachment files

It depends entirely on your ISP's limits on maximum file size of attachments. They are the ones setting the limits. Also remember that not every recipient will have a fast internet connection and may not appreciate having to download a large attachment. Here are iCloud's limits:

Mailbox size and message sending limits in iCloud - Apple Support

I would use a cloud service and send a LINK for downloading at leisure - one such that many use is https://www.dropbox.com/ - it has integration into the Finder = VERY handy

I second the recommendation for Dropbox. My Yahoo will allow me to send up to 25 megs, however not all people can receive files that large.

The one limitation to icloud, I recently had someone try to share photos with me via iCloud but it could only be accessed via an Apple product (I had to use my iPod to download it, then transfer that to my computer to access the files)

So while iCloud may work for some, it does not work for all.

It may or may not be - for instance, in my area, Comcast cable advertises and charges for 25 mbps whereas the reality is: 30 - 35 year old cables and the actual speed usually less than 6 mbps. The only other option is DSL which actually produces what they advertise, but it is not fiber. So, there are areas where a fast connection simply is not available or too expensive and it would be those recipients who may decide to simply not download something that would take too long.