All of a sudden after many years of trouble free use, all of my members with Hotmail/MSN/Outlook email addresses are bouncing back forum notification emails. It looks like Hotmail is either saying some part of my mail service is on a block list or has been determined to be "spammy". Nimbus say they have checked my server IP and it's not blacklisted anywhere (though I just realised I don't use the built in sendmail, I use a proper email account set up at Nimbus, wonder if they checked that, I'll ask). Code: said: 550 SC-001 (COL004-MC5F3) Unfortunately, messages from xxx.xx.xxx.xx weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. (in reply to MAIL FROM command) First question really is to ask if anyone else here has suddenly had an issue with Hotmail, or is it just me? Second question is to ask for suggestions on alternative email services I might use to send out forum emails, is there anything that's more Hotmail friendly? Anything else worth trying? I know this happens a lot, but it's so sudden after no problems, so wondering if anyone else is affected?