iOS devices with iOS 4.2 that connect to the mail server will prompt out the message 'Cannot Verify Server Identity' when send and receive an email. It is because the iOS 4.2 is not working fine with the self-signed SSL Cert.
Below is the step to disable the Use SSL so the message unable to prompt out.
1) Select the Settings
then select the Mail, Contact, Calendars
2) Select the mail that created
3) Select the Advanced
4) Off the Use SSL