Using Zend_Mail_Transport_Smtp with an MD5-Hashed value as password
===

I'd like to offer the users ob my web-application the possibility to send out emails using our smtp-server.

The password for the user accounts are md5-hased and the smtp-server is hashing the received values to check for the right username-password kobination.

Now i'm looking for a good way to set up Zend_Mail_Transport_Smtp - I obviously need the plain-text password and forward it to the smtp-server which then converts it to a md5-hash.
But that means that i have to store the users password somewhere in plaintext, which i'd like to avoid.

Are there any best practices on how to set up an webmailer using the zend framework?

The only idea i had was to save the unhashed password in a session (the user accounts in my application are linked with the mail server accounts), but there has to be a better way to handle this situation