Unread "unsubscribe" emails in Yahoo email sent folder

Bastet said:

Most likely it is spam. They’re hoping you’ll click on the unsubscribe link which will show them the email address is valid. You’d then begin receiving more spam as they’d sell your email address to other spammers.
Do you have any email filter rule to send spam to the junk mail folder &/or automatically send an unsubscribe email? I’d check to see if there’s any automatically send an unsubscribe email option under Yahoo’s email settings.

Thanks for your input. I checked all filters, and there are no custom ones I added. I have clicked on unsubscribe links in the past for what I think were legit emails (mailers I added my email to previously, but now don't want them anymore, but some may have just been spam), and some spam does get to my inbox, and those I manually mark/send to the spam folder to hopefully register the address as spam for the next time, but usually the spammers use unique long strings, so some still get to my inbox.

And just to add this didn't just start. I've notice unread "unsubscribe" emails before (even years ago), but just thought I'd ask around. Like I said I'm the only one signed into my accounts using strong unique passwords, and 2FA.

Bastet said:

Have you checked under the webmail version of the accounts?
It seems Yahoo have an auto unsubscribe option:
Yahoo Mail's 'Unsubscriber' Gets Rid of Unwanted Email Subscriptions
I would check for malware just in case.

Funny you gave that link. I was just reading that from doing a search on any Yahoo unsubscribe features. Before posting here I update virus/malware definitions on both PCs, and did run a full scan to check, but it came back 0 threats found. I also run SuperAntiSpyware from time to time, and it only ever finds tracking cookies. So I don't think it's something malacious especially since both accounts are used separately on two different PC, but yet both show the same type of thing in the sent folders.