You can check the membership of any email list you are a member of.
First visit your mailman server's page http://lists.remc1.net You will see all the lists hosted by the mailman server. Click on the list you are interested in (for this example I am using the uptech list)
A page will load with options to browse the archives of the list, and other list tools. Scroll to the bottom of the page to section entitled Subscribers.
If you know your list password you can enter it along with your email address.
If not, mailman will send you your list password. Scroll down to the bottom of the page, enter your email address and click the "unsubscribe or edit options"
Click on Password Reminder. Your password for the list will be emailed to your email address.
When it arrives, fill it in along with your email address and click on view subscriber list.
A webpage will be presented with all the subscribers of the list.
If you have questions please send email to support@remc1.net