email problem

[skyria]

Hello everyone, I'm skyria, I hope this is the right section.
It's been almost two years I have a web space on webhosthing, and I never had any kind of problem, only that since I added new domains on my space I have problems with e-mails. First, they always bounce back to me on my main web account, with the reason "relaying not permitted", and I can't log onto them without logging on the cpanel.
How can I activate e-mails and log on them without logging onto the cpanel first?
Why do they bounce back?

[Sergey S.]

Dear Skyria,

Have you contacted out technical department at whbsupport.com in a ticket?

Please submit a ticket providing the full headers of the bounced messages. Also provide the domains and email addresses you are trying to send from. Additionally it would be great if you could describe your actions step by step so that technicians can reproduce the issue from their side.