One of my sites serves a monthly newsletter to members. We handle double opt-in, the US can-spam and have Dmarc etc set up, so everything should be above board. It ran fine until this month, when all the hotmail accounts returned it, because hotmail have blocked it. There's no contact details on the rejection, so I can't find out why it is blocked. Does anyone know how to get this type of thing fixed? I have spoken to several of the affected members and they'd whitelisted the address. We have no idea why, after a year with no problems, this has happened. Does hotmail not like .in addresses?