All recipient email servers process Black Listed domains differently.  Some messages are highly cryptic and some are easy to read.  There are no standards; expect anything.

However, generally, black listed error messages usually contain several pieces of information:

1. The sending server's domain
2. The recipient's ISP (Internet Service Provider) that is issuing the "block" (a "block" means you're on the black list)
3. The error message
4. If the ISP has a resolution (how to get off their black list), they will provide a link to the instructions for removal - some ISPs do not include a resolution link, such as Gmail. With Gmail, you can only wait until they decide to clear it - they offer no resolution except the tincture of time.  Not all ISPs provide resolution tools.

1. The sending server is on a Black List - See this help document: What do I do if I'm on a Black List?
2. The SPF Record attached to the sending domain (example: YourCompanyDomain.com) blocks rsvpBOOK.com from sending email that "claims" to be from YourCompanyDomain.com - See this help document: What do I do if I have an SPF issue?
3. The message is considered SPAM by the receiving email server - See this help document: What do I do if messages are going to SPAM?
4. The email address was incorrectly entered by the registrant (a typo) - See this help document: What do I do if the registrant submits an erroneous email address?
5. 100 Spam Trigger Words & Phrases To Avoid