How can I send emails in the background on a WordPress website

[admin]

I a using WishList Member on my wordpress website.

I have created a custom form.

Once users enter their data an email confirmation is sent for them to confirm their email and admin is notified that a user has registered.

These emails are sent slowly so the form submission freezes.

How can I set this up so these emails get put into a cron job so they are sent in the background at a later date?

Thanks

Mitchell