OCI Email Delivery smtp-server: 504 The requested authentication mechanism is not supported

Symptom:

  We plan to use mailx in  Oracle Linux 7.6 VM to send emails via smtp services provided by OCI Email Delivery Service
   We followed the instructions of  the official doc and get smtp credential and smtp connections setup
When we run this command:

echo "test test from henry" | mailx  -v -s "test test test"  \
-S nss-config-dir=/etc/certs  \
-S smtp-use-starttls \
-S smtp-auth=login \
-S smtp=smtp.us-ashburn-1.oraclecloud.com \
-S from="no-reply@test.com(henryxie)" \
-S smtp-auth-user="<ocid from smtp credentials doc >" \
-S smtp-auth-password="<password from smtp credentials doc >"  henry.xie@oracle.com

We get error
smtp-server: 504 The requested authentication mechanism is not supported

Solution:

    Change smtp-auth=login -->  smtp-auth=plain
    Later OCI email delivery will support smtp-auth=login