I'm doing a project at the university where I asked to set up a mail server, for this I'm using Sendmail as an SMTP service, I already configure sendmail.mc correctly and it allows me to send emails to remote addresses, the problem arises when I want to send an email to another virtual machine that I am using to act as a client.
Already configure the virtual machine and between the machines there is connection. I am using Alpine for sending and receiving messages and when I want to send an email from the client to the server I get the following error:
--The following address has permanent fatal errors --
<[email protected]>
(reason: 550 5.1.1 <[email protected]> User Unknown )
I am new to this network and I wanted to know how to solve it, reading I found that it could be an error in the client's hostname.