Spam on an old Yahoo acc

[#1]

Hi, I have an old Yahoo account which I no longer use but I had it set up within Thunderbird to download mail through my Plusnet account. I have for some weeks now been getting a lot of spam mail into the Yahoo mail box, I deleted the account within Thunderbird under account settings but still get it into my in tray through my default  Plusnet account, I'm running the latest Thunderbird 16.0.2.
Could anyone advise if there is another setting I should have removed to stop this happening.
regards
jono

[#2]

Hi, I have sorted the problem, well I hope I have, I looked through my records and found that I rarely use it so I have deleted my account at Yahoo. Sick of getting PPI and other so called money offers, My daughter told me today she is getting inundated with phone calls from these firms.
Regards
jono