Of the problems that can cause this error, they usually are because of some mismatch between a setting on your phone and your email server. There can be a number of errors, so unfortunately the only way to tell is to try several things and see what works.
Method 1: Set up your email again using advanced settings
Go to Menu>Settings>Email & Accounts, long press on your account, and select Delete. Then go to Add an Account, and run through the setup process again, this time choosing Advanced Settings.
Method 2: Correct the time on your device
One common cause is that the time on your device and email server don’t match, which throws out this error. In that case, go to Menu>Settings>Date and Time. Uncheck “Automatic configuration” if it’s checked, and correct the time there. If it’s not working then, check with a system administrator to make sure that the time on the server is set correctly.
Method 3: Install the correct email certificate
The certificate that your phone is using may not be the right one. On another computer that can access your email, Outlook will be set up with that certificate. Save it to your computer, then send it to another email address on your phone. Download the certificate from the attachment and install it. Once it’s installed, you’ll need to delete and reinstall your email account. Go to Menu>Settings>Email & Accounts, long press on the account, and select delete. Then go to Add an Account, and run through the setup process again.
Method 4: Reconfigure input/output ports
Go to Menu>Settings>Email & Accounts, then select the account you’re getting the error with. Go to Settings, then scroll down until you see Outgoing (SMTP). This needs to be the same port that your email server is sending through. The default here is port 25, which is blocked by most ISPs because of how often it’s used for sending spam. Your email server should allow a different one. Contact your system administrator to get which ports you use, and change it that menu.
Method 5: Correct the APN on your SIM
Your phone may be trying to connect to your wireless provider using the wrong Access Point Name. To fix this, go to Menu>Settings>Access Point>Add. Once there, you’ll need to enter the details provided by your wireless provider.
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