How to disable mail queue to store in database?

Hi there!

I've got question about storing mail queue in database.

I don't need to notify my users by emails. So I have this option disabled.

But e-mails are added to my database table and stored there, occupying and growing database size.

My site has more that 1 000 000 views per month, so database optimization is very important for me - how can I delete option to store not sent e-mails in database?

I'll be very grateful for your help!
Best regards!
Adam