How interesting (and you say you're not an email expert!). Your logically outlined explanation is probably right. Subsequent to my post I noticed that Amazon and other emails began appearing in my Hotmail account. OK, it actually took a day or more before they arrived but they did all eventually appear. Now they come through pretty quickly. Maybe Hotmail security just needed to get used to the IP/sender inconsistency. Anyway the difficulty seems to have resolved itself - but it's good to think I now know why! Thanks.