[dejan]

Thank you for the comment and typo correction! Fixed.

> Allowing multiple customers to send mail from the same IP seemed too risky.

There are two sides of this problem. Sending very little traffic from an IP can also have negative effects as it will often be seen as "new". Using a shared range to send out mails of all customers could keep all IP addresses warm. The benefit is also that if there is one bad apple, it is statistically very low.