Hotmail bounce message 421 RP-002

The mail server IP connecting to Outlook server has exceeded the rate limit allowed on this connection. Reason for rate limitation is related to IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help.

Stop all this jibber jabber, what does it mean?

The SMTP server you are using has reputation problems. This can happen because:

your email provider uses a new server that is not (yet) well known by Hotmail
your email provider has had problems with spam, causing this temporary bad reputation

Did I do something wrong?

No. The problem resides on the SMTP server of your outgoing email provider.

How can I fix this?

At this point there is not much you can do. This is a temporary problem and will most likely get solved automatically. Either try sending your email again a little later, or contact your SMTP server administrator.