This error will appear for some users after we upgraded your server because some email clients keep old security data on your device.
To fix this error you should follow the following advice;
- Make sure that your email account is set up as outlined here. Please make sure to check that the server address in particular is entered correctly for both the incoming server and the SMTP server as outlined in that link.
- Toggle the 'Use SSL' option in your account settings. First turn it off and save your account settings, then immediately go back and turn the SSL setting back on
- In Apple Mail there is an option that says 'Automatically manage connection settings' in Preferences->Accounts for each account. Make sure that it is not checked.
- Check to make sure your IP has not been banned. Your IP can be banned if your make too many connections with an incorrect password.
- You may need to delete your email account from your mail client and re-add it in order for your device to remove the stored account details.
- There are two types of email accounts; IMAP and POP. IMAP keeps all your email on our server. POP downloads your email to your device.
- Verify the type of account you have, either IMAP or POP from your account settings in your email client
- If your account is set to IMAP, which is the more popular option, you can safely remove your account from your device and re-add it with these instructions
- If your account is set to POP, there is a chance that your email is downloaded to your computer and removed from the server if you have selected this option to 'remove email from your server' in your email client. You can login to your webmail from your client area to verify if your email is still on our server or check your account settings in your email client for the 'remove email from server option'. If your email is still on our server you can safely delete your account from your device and re-add it with these instructions.
- If you still have problems try using the Connection Doctor window in Apple Mail as outlined here in step 3. It will give you exact errors for why your email is not working.
For Recent Update to iOS 17.7 or iOS 18
If you're still having problems with your Mail app after updating to iOS 17.7 or iOS 18, adjusting the IMAP Path Prefix could be a possible solution.
This minor tweak might improve the your Mail app's ability to locate and sync your emails properly.
How to Adjust the IMAP Path Prefix:
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Open the Settings app on your iPhone.
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Scroll down to the Apps section and tap on Mail.
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Go to Accounts, and then select the email account that's causing the issue.
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Tap on Account Settings, and then select by Advanced.
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Find the IMAP Path Prefix field and try entering either a forward slash (/) or the word INBOX (there might be a default grey slash already in the field).
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Once you've made the adjustment, press the Done button to exit Settings
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Close the Settings app, then reopen Mail.app to check if the problem has been fixed.