We have been unable to use ActiveSync email in our mail app since the IOS 18.2 update. We have repeatedly recreated the account but cannot improve the situation. We have normal access to ActiveSync mail on IOS 18.1.1 and ipadOS 18.2. Is there any additional configuration required in IOS?

https://support.apple.com/en-us/HT211025 I understood from this page that the server certificates of proprietary CAs added by the administrator, such as MDM, are not affected by the shortened validity period. However, I get a warning about server certificate validation and cannot access the service. If there are any other conditions, please let me know. The validity period of the server certificate is "5 years" and windows is not affected.