How do I contact Yahoo about something weird going on in my e-mail?

I keep getting this messages that are going straight into my bulk e-mail box that are really weird. One came from someone I know and the others are coming with weird names and different titles every time (right now I have one from "need" titled "indemnity" and another from "Helen Y.... show more I keep getting this messages that are going straight into my bulk e-mail box that are really weird. One came from someone I know and the others are coming with weird names and different titles every time (right now I have one from "need" titled "indemnity" and another from "Helen Y. Jones" titled "This Finnish company is currently estimated....."I get 2-4 of these a day and have been getting them all week now. When I open them, they have a bunch of gibberish and then talk about stocks (one in particular is ARRS). It is really weird and I don't know if I am being spammed, hacked or there is a virus going around. I would like to report them to Yahoo so they can investigate further but don't know how. Any suggestions or anyone else familiar with these e-mails? BTW, they don't have any way to opt out of them, they have no attachements and I am not going to reply to the e-mails, as I know this can open another can of worms.
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