[Exim] strange smtp delay?

Hello All,

I currently have a problem which has got me very confused!!
EVERY smtp connection to my mailserver takes exactly 30seconds from initial
connection to complete. (as below)

2001-09-06 21:10:24 15f5Tk-0003G4-00 <= removed
2001-09-06 21:10:54 15f5Tk-0003G4-00 => removed
2001-09-06 21:10:54 15f5Tk-0003G4-00 Completed

If you try to telnet to my mailserver on port 25 it also takes exactly
30seconds before I get the mailserver greeting! Its running Solaris 2.7 &
Exim 2.12. Am I missing somthing obvious? I don't know what to check next!

Any help will be very much appreciated.

Regards,
Jason