Can't get rid of this spam: ecare.all.r@emailff.att-mail.com

Please rephrase your question, I'm not getting your meaning. Are you saying you have one particular spam message that can't be deleted? Or that you're getting repeated spam messages from that same address? Both can be dealt with, but in different ways.

Thanx for asking. I meant to say I am getting the same att spam 2 to three times every day. I always mark it as spam and delete but it continues to come back.

If the spam always has precisely the same subject line or From address, you can make a Message Filter that will automatically mark it as spam and move it to the spam folder. Here's an article that details what Filters can do and how to set one up:

https://support.mozilla.org/en-US/kb/organize-your-messages-using-filters

However, your email provider probably has it's own simple filter feature that can do a similar job. The advantage of using that one is that it would catch the spam right away as it's received, and you would never even have to download it.