Inconsistency between APN for Internet on your SIM and the access point in the customer data plan
Do one of the following:
To manually set the corresponding APN, go to the phone menu> settings> Access Point> Add. In the Internet APN field, enter the details provided by your operator.
Update the application access point following the steps in Install or update the application access point in your Lumia.
Incorrect setting the time and date on your device
Check the settings in menu> settings> date + time.
If automatic configuration option is selected, clear and correctly set the time, date and current time zone.
A task calendar is not synchronized with an account exchange.
Generally the date on the server or device is not correct.
Contact your system administrator to check the time and date settings on the server. Such data must be the same on the device. Otherwise, correct the device.
Certificate of missing mail or self-signed certificate expired
Contact your account manager to check the validity of the certificate in use.
Please send by email the certificate to your phone, download and install it.
Delete the account menu> settings> email + accounts> hold particular account> delete.
Reconfigure the mailbox from menu> settings> email + accounts> add an account.
Configuring port input / output Wrong
Do one of the following:
Check the settings of port input / output and correct configuration, and check with the account administrator in menu> settings> email + accounts, hold the particular account and configure the correct ports.
Delete the account and reconfigure using the correct port configuration in / out.