A bounced email message that was undeliverable because there was an error in the email address normally includes 2 pieces of information:

1. The email address that failed delivery
2. The reason it failed - there are many forms of this message: Unrouteable address, Recipient unknown, No such address on this server, etc

There are 2 main reasons email addresses contain typos:

1. The registrant accidentally inserted a blank or some other character that is not allowed in an email address
2. The registrant merely mispelled his/her email address

In either case, if you want to correct the email address, you should call, or otherwise contact the registrant and obtain the correct email address verbally; then edit their record and change it using the Registrant List - How do I edit a registrant's record?

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. 100 Spam Trigger Words & Phrases To Avoid