title: Grafana alerts test notification sent but no email has been received
body: <p>I wanted to test Grafana alerts. I want to receive email when there is an alert. So first I have setup the SMTP in grafana.ini file:</p>
  
  <pre><code>#################################### SMTP / Emailing##########################
  [smtp]
  enabled = true
  host = localhost:25 
  user = 
  # If the password contains # or ; you have to wrap it with trippel quotes. Ex """#password;"""
  password = 
  ;cert_file =
  ;key_file =
  skip_verify = true
  from_address = admin@grafana.localhost
  from_name = Grafana
  
  [emails]
  ;welcome_email_on_sign_up = false
  </code></pre>
  
  <p>In the test in the Grafana, I have set name, type:Email, send on all alerts, include image.
  My email is on hotmail.</p>
  
  <p>When i press send test, I receive Test notification sent, but there is no email received...</p>
  
  <p>Here is the log:</p>
  
  <pre><code>t=2018-07-06T11:09:54+0000 lvl=eror msg="can't read datasource provisioning files from directory" logger=provisioning.datasources path=/etc/grafana/provisioning/datasources
  t=2018-07-06T11:09:54+0000 lvl=info msg="Initializing RenderingService" logger=server
  t=2018-07-06T11:09:54+0000 lvl=info msg="Initializing TracingService" logger=server
  t=2018-07-06T11:09:54+0000 lvl=info msg="Initializing Stream Manager"
  t=2018-07-06T11:09:54+0000 lvl=info msg="HTTP Server Listen" logger=http.server address=0.0.0.0:3000 protocol=http subUrl= socket=
  t=2018-07-06T11:09:54+0000 lvl=eror msg="can't read dashboard provisioning files from directory" logger=provisioning.dashboard path=/etc/grafana/provisioning/dashboards
  t=2018-07-06T11:09:57+0000 lvl=info msg="Sending alert notification to" logger=alerting.notifier.email addresses=[myEmail@gmail.com]
  t=2018-07-06T11:09:57+0000 lvl=info msg="Sending alert notification to" logger=alerting.notifier.email addresses=[myEmail@gmail.com]
  t=2018-07-06T11:10:26+0000 lvl=info msg="Sending alert notification to" logger=alerting.notifier.email addresses=[myEmail@hotmail.com]
  t=2018-07-06T11:10:27+0000 lvl=info msg="Sending alert notification to" logger=alerting.notifier.email addresses=[myEmail@hotmail.com]
  t=2018-07-06T11:12:31+0000 lvl=info msg="Sending alert notification to" logger=alerting.notifier.email addresses=[myEmail@hotmail.com]
  </code></pre>
  
  <p>I have tested with gmail too, and it is same.</p>