With Mailgun, you'll need to upgrade to a dedicated IP or "managed email service" and pay extra for "better deliverability." At Postmark, great deliverability isn't an up-charge. It's simply included, and we share live delivery data so you can judge for yourself.

and one which you don’t need to use and won’t add any code to your app if you choose not to use

And of course, if you don't use them you don't pay for them