MailTo Character Limitation

My customer wants to view the email using MS Outlook before sending with specific information filled in. So I am using mailto. However, unlike the example below, the body of the email exceeds the character limitations so it will not open up the file. What are alternatives or can I someone give them a link so they can copy and paste the body information. Not sure whether you can attach a text document for them to copy from.

<a href="mailto:[email protected][email protected], [email protected], &[email protected]&subject=Mail from our Website&body=Some body text here">Send Email</a>