An email delivery service is pretty much a must have for businesses who want to make sure that their email gets delivered to their customers and that no one can impersonate them by fake email addresses.
From a personal email perspective, however, it might also be a good idea to use an email delivery service. This is especially true if you have a newsletter service or run a blog, for example.
My favorite service is Mailgun. They offer 10,000 free email sends per month, which is more than enough for personal use.