'large amounts' is also pretty relative, I'm sure if you had a small team of 10-25 employees on a self-hosted mail server (preferably with a static IP via the I

'large amounts' is also pretty relative, I'm sure if you had a small team of 10-25 employees on a self-hosted mail server (preferably with a static IP via the ISP) you'd be taken seriously pretty quickly versus only you sending an email once a week or less.