Inactive email users

We have a red hat linux 7.1 server which acts as an email server. Is there a way to track down users who have been inactive for 3 to 4 months. Inactive means that he has not yet opened his mail box for the past 3 to 4 months since the last he openedit. Does this need extra scripting to accomplish this?

Could anyone help regarding this matter. Thanks in advance.

Clem