Occasionally an account owner will keep a web archive of all the emails they send to a list. (We do it here at Simplero).
If you want to access a previously sent email and didn't save it, it's simple. (Note: This is only if the list/account owner keeps the web archive. They can deactivate that option)
Click the “manage your preferences” link on any email that you received from that person:
This will open a page showing the lists you are subscribed to. The lists that have the option to see archived emails will show as hyperlinks that you can click on:
If you click on the list, it will show a list of all emails sent to you on that list: