Getting error message Cannot Verify Server Identity

May I know how long this has been going on?

Please use the below link and follow the instructions to get this issue fixed:-

When Your iPhone “Cannot Verify Server Identity”

1. Restart Your iPhone

   If you receive an alert saying that your iPhone “cannot verify server identity”, the first thing to do is restart your iPhone. This simple step can occasionally fix a minor software glitch that could be causing this error.

   To restart your iPhone, press and hold the power button until you see slide to power off appear near the top of your iPhone’s display. Use a finger to swipe the red power icon from left to right to turn off your iPhone.

   Wait around a minute, then press and hold the power button again to turn it back on. You can release the button once the Apple logo appears at the center of the display on your iPhone.

2. Close The Mail App, Then Reopen It

   When the mail app isn’t working properly, try closing out of the app and reopening it. This can occasionally resolve minor problems if the app’s software crashed while you were using it.

   To close out of the Mail app, double-click the Home button, which will open up the App Switcher. Use a finger to swipe up on the Mail app until it no longer appears in the App Switcher.

3. Delete Your Email Account, Then Add The Email Account Again

   Deleting and reentering your email account information resets your email’s server identity certificates, which allow your email account to be verified by the Mail app. Don’t worry — deleting an email account on your iPhone will not delete your actual email account.

   To delete an email account on your iPhone, open the Settings app and tap Mail -> Accounts. Then, under Accounts, look for the email account you want to delete and tap it. Finally, tap the red Delete Account button at the bottom of the screen, then tap Delete Account again when the confirmation alert appears on your iPhone’s display.

   To add your account back to your iPhone, go back to Mail -> Accounts. Then, tap Add Account and follow your iPhone’s prompts to re-enter your account information.

4. Reset All Settings

   When you reset all settings, all of the data from the Settings app on your iPhone will be erased. Software issues can be difficult to track down, so we’ll reset all settings to make sure we erase the problem completely.

   To reset all settings, open up the Settings app, then tap General -> Reset -> Reset All Settings. If you have a passcode or a Restrictions passcode, you’ll be prompted to enter them. Once you do, tap Reset All Settings when the confirmation alert appears at the bottom of your iPhone’s display.

Please use the below link and follow the instructions to get this issue fixed:-

When Your iPhone “Cannot Verify Server Identity”

1. Restart Your iPhone

   If you receive an alert saying that your iPhone “cannot verify server identity”, the first thing to do is restart your iPhone. This simple step can occasionally fix a minor software glitch that could be causing this error.

   To restart your iPhone, press and hold the power button until you see slide to power off appear near the top of your iPhone’s display. Use a finger to swipe the red power icon from left to right to turn off your iPhone.

   Wait around a minute, then press and hold the power button again to turn it back on. You can release the button once the Apple logo appears at the center of the display on your iPhone.

2. Close The Mail App, Then Reopen It

   When the mail app isn’t working properly, try closing out of the app and reopening it. This can occasionally resolve minor problems if the app’s software crashed while you were using it.

   To close out of the Mail app, double-click the Home button, which will open up the App Switcher. Use a finger to swipe up on the Mail app until it no longer appears in the App Switcher.

3. Delete Your Email Account, Then Add The Email Account Again

   Deleting and reentering your email account information resets your email’s server identity certificates, which allow your email account to be verified by the Mail app. Don’t worry — deleting an email account on your iPhone will not delete your actual email account.

   To delete an email account on your iPhone, open the Settings app and tap Mail -> Accounts. Then, under Accounts, look for the email account you want to delete and tap it. Finally, tap the red Delete Account button at the bottom of the screen, then tap Delete Account again when the confirmation alert appears on your iPhone’s display.

   To add your account back to your iPhone, go back to Mail -> Accounts. Then, tap Add Account and follow your iPhone’s prompts to re-enter your account information.

4. Reset All Settings

   When you reset all settings, all of the data from the Settings app on your iPhone will be erased. Software issues can be difficult to track down, so we’ll reset all settings to make sure we erase the problem completely.

   To reset all settings, open up the Settings app, then tap General -> Reset -> Reset All Settings. If you have a passcode or a Restrictions passcode, you’ll be prompted to enter them. Once you do, tap Reset All Settings when the confirmation alert appears at the bottom of your iPhone’s display.

Please add the email account again after the deletion.

Did you connect with the Apple support?

Please use the below link to connect with the Sprint support:-

https://www.sprint.com/en/support/contact-us.html

They will be able to assist you further.

You're welcome!

Is your issue fixed now?