[Exim] PAM nand SPA

Is the following statement accurate:
"You cannot use the SPA authentication driver with PAM authentication
because exim needs the (authoritative) plaintext password to do SPA
authentication. Therefore, if you are setting up exim to
authenticate MS Outlook users at SMTP time via PAM, then you cannot
use SPA. And if SPA, then not PAM."
(Don't flame my skepticism; I wrote that for this.)