Fixing the Cannot Verify Server Error in iPhone and iOS devices

If you are using an Apple iOS device and the mail client is getting the "cannot verify server identity", then follow the steps below to resolve the problem. It affects both IMAP and POP3 account types but is mainly happening in recent releases of Mac iOS 10.2x. The following solution is based on multiple report/posts from users and Apple support. Note that all of these solutions are based on the fact that you are using SSL for your email.

Fixing the Cannot verify error in the iPhone Mail Client

There are several ways to fix the "cannot verify error". Please follow the directions provided in the solutions listed below

Remove and Recreate your iPhone Mail account

The main suggestion from Apple on correcting this issue is to remove your email account and set it up again. Make sure that you know where your email is saved. If your email account is with Web Hosting Hub, then deleting your email settings in the iOS device will not delete your email. You will be basically removing your email account from your device and then re-adding it.

POP3 Email accounts: If you are using a POP3 account and you have your email set to DELETE in 7 days or when removed from Inbox, then there is the possibility that your emails will be deleted after deleting your account from the iPhone/iOS device. If you have set it to NEVER, then your emails will still be on the server, but you may need to set the fetch to manual in order to get the emails immediately. Otherwise, you may need to wait 15 minutes, 30 minutes, or hourly depending on the setting you have selected in Fetch New data.

1. Log into your iOS device.
2. 

   Go to Settings then tap on Mail.
3. 

   Tap on Accounts.
4. 

   Click on the email account that you wish to remove.
5. 

   Slide the window up and you will see the option to delete the account at the bottom of the screen. Tap on Delete Account.
6. 

   Confirm that you want to Delete the Account or cancel to stop the process

7. Add your account again - Configuring your iPhone for Email.

If you have multiple accounts created on your iOS device, then you will need to remove and recreate them too. You may not see the option to trust the self-signed certificate until all of the accounts have been removed and then re-created.

Emails in Outbox

If you have unsent emails that are in the Outbox, then you may need to remove the outgoing emails and re-send them. If you don't see an Outbox, then you do not have any emails that unsent.

How to turn off SSL in an iPhone Mail account

Although you can turn off SSL as an option in the email client interface to avoid the issue, the use of SSL for emails is preferred.

Although it is not recommended, you can turn off the use of SSL and the error regarding verifying the server will go away. You should only do this if you have an immediate need to get to your email. Here's how you turn off SSL in the iOS Mail client:

1. Log into your iOS device.
2. Go to Settings then tap on Mail.
3. Tap on Accounts.
4. Click on the email account to select it
5. Click on label for your mail account again - it will be above the Mail and Notes icon
6. Click on Advanced
7. Click on the slider that is labeled Use SSL. It should not be marked as green.
8. Click in the top left corner where it says Account.
9. In the top right corner click on Done.

Saving these settings will remove the use of SSL from the iOS account and should also remove the verification error.