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We suggest that this attribute contain a password that a token that can only be used for the current login session. Passing in a plain-text password via UserInfo is probably not a good idea (for example- what if there were something outputting UserInfo to the screen for debugging purposes in another portlet- then the mailpassword would show up on the screen).
Integrating with Your SSO
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First discuss with your provider's mail server support about how you could provide a ticket to use as the password to the POP/IMAP server, so that the portlet (the server) could request email from that mail server, with the intent being for the MailPortlet to display the users' mail message subjects, senders, and datetime sent (and it supports display of a few standard IMAP flags). Webmail is totally separate from this request. While the user's HTTP/HTTPS request to the portal may contain the information needed to authenticate to the mail server, when it gets to the portlet itself, the portlet is making a connection to the POP/IMAP server (via JavaMail, which the portlet makes fully configurable to connect however you want, but typically is via POP3/POP3S/IMAP/IMAPS) and to connect and retrieve mail, it will require a username and password of some sort, the username being the user's mail account username most likely, and a password (in this case, a ticket).
Then you want to determine how you are going to provide that ticket to the portlet. If you use UserInfo to do it, use that class in the config (that's what you would use with Shibboleth for example).
If needed (probably not) you can write your own java class to assist with authN and/or password encryption. The MailPortlet is customizable and pluggable, and all JavaMail properties can be configured per account if needed, so the options are pretty wide-open (if you find a way to get the authN info to the portlet, it can fully utilize the JavaMail to do whatever JavaMail can do to get messages from whatever source you want- JavaMail is also pluggable for non-standard message protocols).
CSS
We tried our best to use some sort of uPortal standard styling that would be most compatible with existing and custom skins.
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