Every email provider is different when it comes to attachments. They may allow for a larger attachment to be sent then received (or vice versa). Not only does the outgoing server must support your email size, but the receiving server must also be able to receive the file size. In addition, this increases the size of the email, and means more data is used to get the email. This maybe a hard pill to swallow with someone on a limited data plan.
With that being said, I have chosen to do something completely different, and something that might be unusual to some. I have fsp.zip which I will upload your files to that domain. If I have multiple files to send to you, I will combine it all in a .zip file, and upload it. I will then give you the URL to the file so you can choose to download the file when it is convenient for you. I will usually keep the file online for 30 days, or until you tell me that you receive the file. It’s not intended to be a storage system as services like Dropbox, or Google Drive can do that. I feel this is the best solution, and will stick with it.