[Mashiro]

Oh! Yes, sorry. I forgot to mention that Microsoft, Google and probably also other providers use their own internal blacklists that have no public blacklist checking API. The only way to check in that case is try to send mails to e-mail addresses hosted at these companies.

It can be hard or impossible to get off those list. Neither Microsoft nor Google are really cooperating on what the issue is, how to properly fix it and how to get delisted. It's a hard job to keep your IP space off the list of such providers.