External mail server is used.
Scheduled notification message is not sent to email. There is an error in Event Viewer:
IDispatch error # 17 (COM Error 80040211, Description: Unable to send the message to the SMTP server. Transport error code: 0x80040217. Unknown server response error: not available ) at Unable to execute event at (runTask :: start line 212) Execute file name: C: \ Program Files (x86) \ Parallels \ Plesk \ admin \ bin \ runtask.exe
Incorrect External SMTP Server settings is specified in Plesk->Tools and Settings->Mail server settings.
Configure a valid email account in Plesk > Tools & Settings > External SMTP Server Settings.