I would second what Farmer17 said below:
I won't send it directly with emails. If you need your bitcoin urgently I would suggest you to ask someone to further encrypt the file (using 7zip, winrar, or whatever software you trust) before sending it, and ofc don't include that encryption password in the email.
A password-protected wallet put inside a password-protected ZIP file is double security. Then you can send it over the email. Of course, don't include the ZIP password in the email, just ask over the phone.
And if you're still paranoid: when you receive the wallet, you can transfer the funds to a new address immediately to start with a fresh wallet.