Message walls are not meant to be part of Fandom's official support features. There is a high chance they will just tell you to submit a ticket instead as they have done to many other users in the past who tried to report issues using staff members' message walls. Message wall greetings are not supported on UCP but, on legacy, MisterWoodhouse's message wall greeting was this:
You must read this disclaimer
My personal message wall is not a support channel for inter-wiki conflicts, account issues, or tech support. Please contact Fandom Staff with these issues.
This is also not a place for you to personally ask for Unified Community Platform details. Please ask such questions on the relevant blog posts after reading the existing comments. It is simply not feasible for me to keep answering all such questions here, especially when many answers are already available in the comments of said blogs.
If you have scrolled down to send me a message, please scroll back up and confirm you read the disclaimer.
Edit: You don't have to have an email to use Fandom but I honestly don't see why people wouldn't have one. If you don't have one because you aren't allowed to, most chances are you aren't allowed to be on Fandom in the first place. If you are of the age where you are allowed to be on Fandom, most people already have an email to contact their friends or for school or for work. If users choose to not have an email out of concern for information privacy, I fail to see how Fandom is any more secure than an email service.