Nevermind. this was a broken script sending no actual username or password, during AUTH LOGIN .. it was sending blank lines..

I'm seeing this when I attempt to debug authdaemon logging:

May 29 22:21:58 serv-pbx authdaemond[6533]: received auth request, service=exim, authtype=login
May 29 22:21:58 serv-pbx authdaemond[6533]: authuserdb: trying this module
May 29 22:21:58 serv-pbx authdaemond[6533]: Unsupported authentication type: login
May 29 22:21:58 serv-pbx authdaemond[6533]: authuserdb: REJECT - try next module
May 29 22:21:58 serv-pbx authdaemond[6533]: authpam: trying this module
May 29 22:21:58 serv-pbx authdaemond[6533]: incomplete username or missing password
May 29 22:21:58 serv-pbx authdaemond[6533]: authpam: REJECT - try next module
May 29 22:21:58 serv-pbx authdaemond[6533]: FAIL, all modules rejected