+1 to not only upgrade Roundcube but to make it the default webmail app.
I have a folder with 15K+ messages in it and SquirrelMail takes forever to display it, even if it's only displaying 25 messages per page. Roundcube shows it quickly so I immediately switched my default to Roundcube. This suggests that SquirrelMail is terribly inefficient and by forcing everyone to use RoundCube means more efficient servers equals happier customers.
And regarding the old suggestions option: I went to contact support about this topic; went to "Feature request/suggestion" and the "tips for this category" say:
Be sure to check if your suggestion is already listed at the Suggestions area. [color=#006400](obsolete: link here brings you back to contact support)[/color]
Submit your suggestion through that page, and other customers will be able to vote on it. [color=#006400](again, obsolete)[/color]
Visit the wiki for information on Suggestions. [color=#006400](this is how I eventually discovered this suggestions forum)[/color]