Address in mailbox given [alterfamily.rbcsolutions.ca] does not comply with RFC 2822, 3.6.2.
That is the answer. You are using your domain name in a setting that should be a valid email address. Check your Mail configuration in kiwitrees.
I’m not sure if it will be in Administration > Site administration > Site configuration > Mail configuration tab > Sender email
or Administration > Family trees > your family tree > Contact information tab > Kiwitrees reply address
I normally have the same in both of those.