Idea Summary
The APEX_MAIL API does not offer a parameter to be passed through to the core UTL_SMTP procedure regarding what SMTP authentication scheme to use. By default UTP_SMTP uses ALL_SCHEMES (CRAM-MD5 PLAIN LOGIN) which is a problem to configure APEX Instance Email with SMTP TLS SSL authentication when the SMTP Server offers only one authentication scheme (e.g. LOGIN).

The idea is to:

- add the SMTP Authentication Scheme parameter to the APEX_MAIL API
- enhance the APEX Instance Settings GUI (Internal Workspace → Instance Settings → Email) to allow the selection of the SMTP Authentication Scheme.

Use Case
- APEX Instance is not able to authenticate to the SMTP Server which accepts only the LOGIN authentication scheme. The issue was analyzed by Oracle Support with SR 3-29456559351.

BEGIN apex_210200.wwv_flow_mail.push_queue_immediate('Y'); END;
*
ERROR at line 1:
ORA-29278: SMTP transient error: 421 Service not available
ORA-06512: at "SYS.UTL_SMTP", line 57
ORA-06512: at "SYS.UTL_SMTP", line 140
ORA-06512: at "SYS.UTL_SMTP", line 641
ORA-06512: at "APEX_210200.WWV_FLOW_MAIL", line 156
ORA-06512: at "APEX_210200.WWV_FLOW_MAIL", line 1690
ORA-06512: at line 1

Preferred Solution (Optional)
An optional solution would be to force the default behavior of the UTL_SMTP package to use a different default value for the SMTP authentication scheme.