@MicrosoftHelps Anyone testing your form would see that it has a problem. Searching the web shows people complaint about this for over 5 years. Iβve requested a delist via my hosting provider instead.
@MSFT365Status@microsofthelps The Delist Portal at https://t.co/LiMElb3BeK seems permanently broken ("Our messaging service has experienced a temporary issue"). Is there another way to submit a delist request?
For anyone interested, I had to buy a new domain name to achieve this. SpamAssassin penalises some TLDs for being "suspicious" including .pro (entirely statistical, but very annoying)