Yes, you need to associate an email address to your MATLAB Central account to be eligible to download a trial release. Trial releases are a sales strategy, and Mathworks would want to be able to send you sales information about the trial.
However, trial releases are not available for versions that old, as mentioned for dbp. Trial releases for anything before the most recent release have to be processed through Mathworks Sales, which would very likely want an email address.
As mentioned by dbp, Standard and Education licenses perpetual licenses, or current Standard or Educational term licenses, entitle you to use any previous MATLAB release for the duration of the term. It is not entirely clear whether Home licenses are entitled to use MATLAB releases from before Home licenses were created. It is not clear whether Student licenses are entitled to use previous releases, but the guideline for those has generally been that if you can get a copy of the old installer than you can use it with your Student license.
Installation of licenses from before R2011a may require the assistance of Mathworks Support as those had a different license key setup.
