Last week it was Xtra blocking outbound mail at reception. This week any message having a Xtra or Yahoo address in the From header is being rejected upon receipt from our listserver, despite the listserver using its own address in the envelope & in the Sender header. When I follow the URL in the quoted SMTP responses, it turns out that Yahoo think I should change my listserver so that the senders address does not appear in the From header. Which sucks, because we already put the listserver's own address in the Sender header (which most mail clients will then render as "From knitting circle on behalf of Jane Smith"), and as far as I know, we're following the RFCs to the letter. So have I missed something in the RFCs that permits Yahoo to do this? They're essentially saying "we don't permit our subscribers to subscribe to mailing lists unless the mailing list is deliberately broken". -Martin