[Exim] sender verification silly with fetchmail

    Well, I have been doing sender verify callbacks and getting the same few messages

    rejected again and again.  
    I dropped sender_verify_max_retry_rate down and down. 

    I noticed that all but one of the callback failures was because I could not
    connect.  nmap showed "filtered" for port 25.

    Then it occurred to me.  Why am I doing this at all when I am using fetchmail to
    get my mail from my ISP?  Who am I telling to "try again later?"  

    Is there a way of deleting this mail from my ISP inbox if callback fails?  
    Can I expect some to be blocking my connection since I am on a leaf node?

    Can I add a header to filter on if verification fails?    

    Thanks,
        Michael