You need to add SMTP account only if your mail domain is hosted with Doka panel and not redirected to a third party mail provider.
All SMTP servers managed by Doka panel require passing SMTP authentication before user will be able to SEND email.
SMTP authentication is additional security measure and it is not a substitution for POP3 authentication, which is required for user to RECEIVE mail.
Single SMTP user may be used with multiple mailboxes.
To add a SMTP account:
Login at Doka panel. in "User menu" navigate to "User -> Managed products -> Email -> SMTP accounts”.
Enter account name. Type in password and password confirmation and click “Add new SMTP user”.