You won't have a "blocked senders list", unless you set one up yourself within a Message Filter. Check your email provider's spam filter, which will usually divert suspicious messages into a ''Spam'' or ''Bulk Mail'' folder and in some cases it may be named ''Junk''. It may be helpful to check the account through your provider's website. Thunderbird's own built-in Junk Controls work by counting how many times words appear, and correlating those appearances with the classification applied by the user as part of the Junk training. The Junk Controls don't take any notice of the "from" address as it is generally spoofed in spam messages.