AAM 2 sites one 3 digit and one 4 problems

[bpowel]

I have 2 sites on our AAM one is a 3 digit extension dial plan the other is 4. The trusted server has 4 digits with a range of 1000-9999. When adding 3 digit mailboxes I have to use 4 digits in the mail box so MWI isn't working. What setting am I missing so I can use 3 digit mailboxes? We have AAN 6.2

[kennethleemeans]

And the 3 digit site is set for 3 digits right ? It may be better to upgrade to 6.3 as the site setup is vastly improved over the 6.2