Mailgun users - use SMTP credentials, not API

The link in the credentials template goes to the Mailgun API page but Jumpstart uses the SMTP method for sending emails, not the API method.

This had me foxed for a while until I realized what was going on. You need to use the SMTP credentials on this page: https://app.mailgun.com/app/sending/domains/<YOUR_MAILGUN_DOMAIN>/credentials

As per Mailgun docs, your SMTP password is only displayed once when you create an SMTP user but you can reset it at any time.

Good call. I had issues with this too. 

I also had trouble getting it to work with Mailgun because I setup my domain in EU region.
Currently the smtp address is hardcoded as "smtp.mailgun.org" in Jumpstart but for EU domains it needs to be "smtp.eu.mailgun.org".

Maybe this should be an optional credential that can be passed for Mailgun too.

At some point soon, I'd like to actually swap these with the API integrations which are a bit better. I imagine they'd have less issues across regions and things.