You can use the following parameters in the oebpsemail.properties file and set the user name and password to enable the sendemail authentication in BP Server.
oebps.email.outgoing.server.user
oebps.email.outgoing.server.password
If the user name and password values are blank or null, then no authentication check is performed. Applications can make use of the new constructor of the SendEmail class to send an e-mail with authentication.
oebps.email.outgoing.server.user