3651931 - Mail receiver adapters fails with NullPointerException null object loaded from local variable 'statusline'

When attempting to connect to target mail server, the PI channel returns one of the below errors:

"Message processing failed. Cause: com.sap.aii.af.sdk.xi.srt.BubbleException: Failed to call the endpoint [null "null"]; nested exception caused by: java.lang.NullPointerException: while trying to invoke the method java.lang.String.length() of a null object loaded from local variable 'statusline'"

Or:

"com.sap.aii.af.sdk.xi.srt.BubbleException: Failed to call the endpoint  [null "null"]; nested exception caused by: java.lang.NullPointerException
at com.sap.aii.af.sdk.xi.net.SMTPClientConnection.sendStartTLSMail(SMTPClientConnection.java:1879)
at com.sap.aii.af.sdk.xi.srt.xmb.XMBMailCallerService.call(XMBMailCallerService.java:794)
... 97 more
Caused by: java.lang.NullPointerException
at java.util.Hashtable.put(Hashtable.java:461)
at java.util.Properties.put(Properties.java:266)
at com.sap.aii.af.sdk.xi.net.SMTPClientConnection.createMailSession(SMTPClientConnection.java:1996)
at com.sap.aii.af.sdk.xi.net.SMTPClientConnection.sendStartTLSMail(SMTPClientConnection.java:1867)"

Or:

[EXCEPTION]
com.sap.aii.af.lib.mp.module.ModuleException
at com.sap.aii.adapter.mail.ejb.XIMailAdapterBean.process(XIMailAdapterBean.java:521)
at com.sap.engine.core.thread.impl3.SingleThread.execute(SingleThread.java:185)
at com.sap.engine.core.thread.impl3.SingleThread.run(SingleThread.java:302)
Caused by: com.sap.aii.af.sdk.xi.srt.BubbleException: Failed to call the endpoint  [null "null"]; nested exception caused by: java.net.UnknownHostException: -host-
at com.sap.aii.af.sdk.xi.srt.xmb.XMBMailCallerService.call(XMBMailCallerService.java:898)
at com.sap.aii.af.sdk.xi.srt.TransportBubble.onMessage(TransportBubble.java:50)
at com.sap.aii.adapter.mail.service.XIMailAdapter.call(XIMailAdapter.java:1054)
at com.sap.aii.adapter.mail.service.XIMailAdapterServiceFrame.call(XIMailAdapterServiceFrame.java:158)
at com.sap.aii.adapter.mail.ejb.XIMailAdapterBean.process(XIMailAdapterBean.java:279)"

Product version: SAP NetWeaver 7.5
System managed by: onPrem

STARTTLS, PI/PO, Netweaver 7.5, SMTPClientConnection, null, NullPointerException, statusline, mail, smtp , KBA , BC-XI-CON-MAI , Mail Adapter , Problem