Error in MAIL parameter RECIPIENT or SENDER; return code &

What causes this issue?

An error occurred in the SAPconnect function when determining the
device type for formatting a document with DEVICE=MAIL.
SX_ADDRESS_TO_DEVTYPE
The function provides the return code specified in the message.

System Response

SAPscript form printout was terminated.

How to fix this error?

Check the values used for parameters MAIL_SENDER and MAIL_RECIPIENT, as
well as the SAPconnect installation.

Error message extract from SAP system. Copyright SAP SE.