We spent some time testing Salesforge around cold email campaigns, and the deliverability side is probably where the product earns its place.
Having email warm-up, address validation, multiple inboxes, and campaign sending in the same workflow removes quite a few steps that normally have to be handled separately. The personalization is useful too, particularly when sending at higher volumes without making every email look like the same template with a different first name.
The setup is fairly straightforward once the inboxes and campaign rules are in place.
Infraforge