How to select an email delivery service

In the case that you decide to go with an email delivery service, there are some things that you should consider:

Pricing – pay by month, pay by emails sent, lifetime license? If you send infrequently, the third option might be more cost effective.
Do they fight against spamming activity?
Do they have at least one staff person who actively works with blacklists and whitelists? Can you talk to them?
Do you like their reporting tools?
Do you like working with their application?
Who are their customers? In addition, you might even ask for references, if that is important to you.