It is common practice to store variable information (like username and password
for logging into SMTP account) in web application init-params or context params,
in order to not recompile JSP pages when such information changes. It would be
very nice to have an ability to provide username & password dynamically to
Mailer tags, for example, in the following way:

<mt:mail ...>
 <mt:user><c:out value="${initParam.SMTPUser}"/></mt:user>
 <mt:password><c:out .../></mt:password>
 ...
</mt:mail>

This seems to be the only suitable way, because Mailer taglib does not support
JSP EL to pass parameters to tags dynamically.
JavaMail 1.2 API provides a way to set default username via mail.smtp.user
property (if we pre-configure mail session instance and resolve it via JNDI),
but no property exists for setting default password.