@cwebber Should be a fairly simple automated process to get delisted. Note that if your IP is marked as being part of a "dynamic IP range", Microsoft will probably block it, regardless of whether or not it's been used for spam. Are you in SORBS DUHL list? http://www.sorbs.net/listing/aboutlistings.shtml
@ocdtrekkie Thanks for that... I don't appear to be in that list...
@cwebber Oh, and https://mxtoolbox.com/blacklists.aspx is a much more wide place to check than Spamhaus.