Using an external service for delivering your emails can take a lot of load off your shoulders if deliverability is a must. Services like Sendgrid and Postmark have pre-configured, whitelisted servers so that your email ensures passage by spam sifters. However, such services are generally pretty expensive, too, especially if you are a high-volume sender.
Do you use an email deliverability service? If so, what service? Why or why not?
Having whitelisted servers is a minor plus, but why aren't your own servers whitelisted? In addition, isn't there a large chance that a servce sending emails for thousands of different compaies is going to attract a spammers?
Finally, whitelisting servers says nothing about your actual email content. Most spam filers look at the actual content of the message. If your content is considered bad, your email is spam no matter who sent it. Many spam filters these days consider any delivery URL to be spam, shich makes it a challenge to send software delivery emails.
We send our delivery emails from two independent email servers to ensure delivery.