How do ITurn off SPAM filter

I RECEIVE occasional emails my Thunderbird, but am not able to forward them, as I get a window saying Charter says they are SPAM. I can go to Charter.net to my account from which my emails come into Mozilla Thunderbird and forward them just fine. SO, Charter tells me I must look to you to see why I am getting this window. Is there a way for Thunderbird to disable the SPAM filter. Nothing in the Junk Filter seems to speak to this. I will thank you forever if you can do this. It is so annoying. The mail comes in okay, NOT being labeled as SPAM, just when I want to forward it to someone is it denied.