3233507 - ERROR: During SUM Mail Notifier startup

The following error occurs while starting up the SUM Mail Notifier 

/usr/sap/<SID>/SUM/jvm/jre/bin/java -jar /usr/sap/<SID>/SUM/abap/mailNotifier/MailNotifierApp.jar properties=/usr/sap/<SID> /SUM/abap/mailNotifier/MailNotifierApp.props
[02.06.2022 11:49:32]    INFO SumMailNotifier (Version 2.1.1) - starting ...
[02.06.2022 11:49:32]    INFO Reading properties from classpath "com/sap/lm/sl/upg/notifier/MailNotifierApp.props"
[02.06.2022 11:49:32] WARNING Properties resource file "com/sap/lm/sl/upg/notifier/MailNotifierApp.props" not found
[02.06.2022 11:49:32]    INFO Reading properties from file "/usr/sap/<SID>/SUM/abap/mailNotifier/MailNotifierApp.props"
[02.06.2022 11:49:32]    INFO Requesting missing mandatory properties:
[02.06.2022 11:49:32]    INFO Properties "SumMailNotifier Properties"
[02.06.2022 11:49:32]    INFO     check.bucket.tries = "1"
[02.06.2022 11:49:32]    INFO     check.dialog.tries = "5"
[02.06.2022 11:49:32]    INFO         check.interval = "60"
[02.06.2022 11:49:32]    INFO       check.max.failed = "128"
[02.06.2022 11:49:32]    INFO             mail.debug = "false"
[02.06.2022 11:49:32]    INFO              mail.from = "<email address>"
[02.06.2022 11:49:32]    INFO              mail.host = "<mail host>"
[02.06.2022 11:49:32]    INFO              mail.port = "25"
[02.06.2022 11:49:32]    INFO               mail.pwd = ""
[02.06.2022 11:49:32]    INFO                mail.to = "<email address>"
[02.06.2022 11:49:32]    INFO              mail.user = ""
[02.06.2022 11:49:32]    INFO             properties = "/usr/sap/<SID>/SUM/abap/mailNotifier/MailNotifierApp.props"
[02.06.2022 11:49:32]    INFO               sum.host = "localhost"
[02.06.2022 11:49:32]    INFO               sum.port = "1128"
[02.06.2022 11:49:32]    INFO                sum.pwd = ""
[02.06.2022 11:49:32]    INFO                sum.sid = "<SID> "
[02.06.2022 11:49:32]    INFO                sum.ssl = "false"
[02.06.2022 11:49:32]    INFO               sum.type = "sumabap"
[02.06.2022 11:49:32]    INFO               sum.user = "egtadm"
[02.06.2022 11:49:32]    INFO SUM Monitor Request URL = http://localhost:1128/slp/sumabap/<SID>/monitor
[02.06.2022 11:49:32]    INFO Starting check request ...
[02.06.2022 11:49:32]    INFO Check request successful :
[Fatal Error] :1:1: Premature end of file.
[02.06.2022 11:49:32]   ERROR SumMailNotifier (Version 2.1.1) finished with errors
com.sap.lm.sl.upg.notifier.MailNotifierException: org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Premature end of file.
        at com.sap.lm.sl.upg.notifier.SlpMonitorRequestFactory.build(SlpMonitorRequestFactory.java:58)
        at com.sap.lm.sl.SumMailNotifier.(SumMailNotifier.java:198)
        at com.sap.lm.sl.SumMailNotifier.main(SumMailNotifier.java:542)
Caused by: org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Premature end of file.
        at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:262)
        at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)
        at com.sap.lm.sl.upg.notifier.SlpMonitorRequestFactory.build(SlpMonitorRequestFactory.java:48)
        ... 2 more

SUM, mail, notifier, lineNumber, columnNumber, Premature end of file, ERROR SumMailNotifier , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , Problem