How come "suggested" addresses keep popping up even after I delete them?

When I begin composing an email, in the "to" field when I type the first letter, 5 email addresses who have been on mailing lists I was on pop up. Clicking the X next to one used to delete it; now it deletes it and comes right back

I'm sorry to hear that you're having some trouble with the addresses that are suggested to you when composing an email in Yahoo Mail. Clicking the X that you describe should remove that address from the list of suggestions. However, if you do send another email to that address after doing so it will start appearing again as a suggestion.

Please contact our email support team directly if this is happening with addresses that you aren't continuing to use. You can contact that team at the link below. Please choose 'Contacts' and 'Manage contact lists' as the categories when filling out the help form.

https://io.help.yahoo.com/contact/index?page=conta...

What do you actually mean?