HELP CAN'T DELETE EMAIL AND COOKIE!!!!!!

I have a mac using Sierra 10.12.3. I use safari.

I can’t get rid of an email from my in box. I have repeatedly deleted it, but it keeps coming back. See attachment.

The email is in German.

Associated with the email is a cookie in the cache ui-portal.de. I’ve deleted this cookie several times, but it keeps coming back.

I’ve run the free avast virus scan several times, it does not pick it up.

I’ve cleared my search history.

I went to finder, go, then library and searched for any .de, but I can’t find anything.

PLEASE HELP!!!

Thank you.

Delete the mail from the server.
Login through web mail and delete it.

Thank you for the prompt reply.

I don’t know what webmail is. Can you send to me a link for webmail. Thank you.

The link depends on who your mail provider is.
Look it up at their website or ask them.