Novell NetMail 3.5.2e
Unable to send outbound email using NetMail.
Mails are piling up in the spool directory.
Unable to send mails to internal users.
Able to receive mails from Internet.
Click on the NetMail Messaging Server Object.
Change the setting in the Host Server Field to IP Address and test.
In this case the Host Server Name was incorrect and the DNS server was not able to resolve it.
Restart NetMail after changing the field.