Failed to send notification to email: connection refused

Im trying to send a test alert via E-Mail to my contact endpoints but keep geeting the same error.

Failed to send test alert.: failed to send notification to email addresses:
bla@bla.com_ dial tcp ip:port: connect: connection refused

I just configured my smtp server and it seems like something went wrong. Can you give me a hint where to look ?

Have you enabled SMTP in grafana.ini?

[smtp]
enabled = true

What are the errors in grafana.log?