AOL email servers automatically reject all incoming 3rd party email domains that start with AIM or AOL (e.g. an email coming from "info@AimAssociation.com" or "admin@AolAssociation.wildapricot.org" is not allowed). This means if your primary Wild Apricot domain starts with AIM or AOL (as in AimAssociation.com), Wild Apricot will use @AimAssociation.com as the FROM email for all outgoing emails, and all emails to anyone on AOL will bounce as a result for using an "unauthorized IP".
To send emails to contacts with AOL email addresses, make sure your FROM email and REPLY-TO email domain do NOT start with @AIM or @AOL. You can check the current FROM email and default REPLY-TO emails in Organization details.