Access to POP3/IMAP4 services is determined by the class of service in which they are a member. By default, all users are members of the default class of service, which gives them POP3 and IMAP4 access.
If you changed the default class of service to exclude POP3 or IMAP4 access rights, or if you defined additional classes of services that do not provide POP3 or IMAP4 access rights, you might want to evaluate your currently defined classes of service to ensure that they provide the appropriate POP3 or IMAP4 access. For details, see Section 29.5.1, Controlling User Access to the Internet.