Not receiving email send from another container

I was wondering if anyone could assist. I am receiving all external emails with no problem, however, when sending a test email from another container holding website this email does not land in my mailbox - the same test email goes to Gmail and other external mailboxes without any problems. I am a little bit stuck and would appreciate any help to solve the issue. What I am trying to achieve is to have a contact form on y website container to be able to send emails.