Mail Client

A mail client is any system that receives mail on a mail server and does not have a local /var/mail directory. This is known as the remote mode. The remote mode is enabled by adding the OR option in the sendmail.cf file.

You must check that the mail client has the appropriate entry in the /etc/vfstab file and a mount point to mount the mailbox from the mail server. Also make sure that the alias for the client is directed to the mail server's host name not to the client's.