Search the Logfile
Various actions are logged for your account, including subscriptions, unsubscriptions, mailings, etc. Typical log entries look like this:
2009-02-18 17:31 post from bklunz@databack.com 2009-02-18 17:35 post from bklunz@databack.com 2009-02-18 19:04 post from byronl@fastmail.fm
Search the log to see various actions; for example:
To see posts in Feb 2009, search for 2009-02.*post
The search is not case-sensitive.