Supporting gobal smtp gateway usage

tmpl/alertmanager.yml

@@ -1,16 +1,28 @@
 global:
   # The smarthost and SMTP sender used for mail notifications.
+%if %%alSMTPUseSys ==  'oui'
+  %if %%tls_smtp == "non"
+  smtp_smarthost: '%%exim_relay_smtp:25'
+  %elif %%tls_smtp == "port 25"
+  smtp_smarthost: '%%exim_relay_smtp:25'
+  smtp_require_tls: true
+  %else
+  smtp_smarthost: '%%exim_relay_smtp:465'
+  smtp_require_tls: true
+  %end if
+%else
   smtp_smarthost: '%%alSMTPHost:%%alSMTPPort'
   smtp_from: '%%alFrom'
-%if %%getVar('alSMTPAuth','non') == 'oui'
+  %if %%getVar('alSMTPAuth','non') == 'oui'
   smtp_auth_username: '%%alSMTPUser'
   smtp_auth_password: 'alSMTPPass'
-%end if
+  %end if
 
-%if %%getVar('alSMTPTLS','non') == 'oui'
+  %if %%getVar('alSMTPTLS','non') == 'oui'
   smtp_require_tls: true
-%else
+  %else
   smtp_require_tls: false
+  %end if
 %end if
 
   # The auth token for Hipchat.