Weird problem with SMTP

[helmer.co]

Hello all,

I am having a weird problem with SMTP. I have been using smtp.google.com for several months without problem. I decided to switch to smtp.mailgun.org. When I do a email test I get an error. But here is the weird part, if I change the name and password back to my gmail ones, it works fine. In fact, using my gmail credentials, I can use ANY name in the smtp field and mail is sent fine!

Any thoughts on why the smtp server is not changing from stmp.google.com to my host?

John