How to resolve ScriptRunner Error Message "ERROR:root:Connection unexpectedly closed while sending mail to..."?

ERROR ScriptRunner - stderr from '/opt/splunk/bin/python2.7 /opt/splunk/etc/apps/search/bin/sendemail.py "results_link=http://localhost.localdomain:8000/app/Splunk_CiscoISE/@go?sid=rt_scheduler__admin_U3BsdW5rX0Npc2NvSVNF__RMD5f595461cdff80ada_at_1591190776_4988.58" "ssname=CISE_Passed_Authentications" "graceful=True" "trigger_time=1591192208" results_file="/opt/splunk/var/run/splunk/dispatch/rt_scheduler__admin_U3BsdW5rX0Npc2NvSVNF__RMD5f595461cdff80ada_at_1591190776_4988.58/results.csv.gz" "is_stream_malert=False"': ERROR:root:Connection unexpectedly closed while sending mail to xx@qq.com