Your assumption that they use more than one domain by accident due to a lack of coördination is not correct. Separating, e.g. your product email from your mailing list email from your corporate email has a number of benefits.

Anyway, I already mentioned a solid incentive for them to use the correct token. Go back and read my earlier comment.

It is correct at least in some cases. https://news.ycombinator.com/item?id=45190323