Mail sent on behalf of AOL Mail users to DMARC compliant domains will be rejected by those domains unless the mail passes SPF and/or DKIM authentication checks AND the domain(s) used in those checks match aol.com.
To resolve this issue, please change your email address in Mhelpdesk to anything other than AOL or Yahoo.
To edit your email address:
4. Select staff member
5. Edit email field
You may also need to update your company email address:
2. My Company
Yahoo: Policy Change
Additional Information on DMARC