Sun Cobalt Qube 3

We have a Qube 3 on our network which acts as our gateway and mail server and I hear it has been in use for about 10 years. It worked fine until recently when it started to hang, slow down our connection and delay mail receipt and then it would pick up after a reboot. We got a spare to use in it’s place and it worked fine for a while but now we receive mails an hour or more after they were sent. Any1 have any idea what we can do about the two qubes?