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Email Error Messages - What Do They Mean?

Every mail server is unique, and so are their error responses. It's not always easy to decipher what they're trying to tell you, so we've collected a list of the most common error messages and their variations so you can figure out what to do about it. Look for the error message that most closely matches the one you received.

"IP Address Has Changed!"

Every time you log into your webmail account, your computer's IP address is recorded. If your IP address changes while you're logged in, webmail won't recognize your new connection as valid and will automatically log you out. The easiest way to fix this error is to log in again so your new IP address is recorded. But if you're seeing this error frequently, here are a few other things you can do:

  • If possible, try using another internet connection, such as a mobile data or a WiFi, and try again.
    • If this resolves the issue, contact your internet service provider and ask to be given a static (unchanging) IP address so it won't change while you're logged in to webmail.
    • If that isn't possible, ask if the "DHCP lease time" can be increased, which will allow your login sessions to be longer.
  • Is the problem only with your webmail client? Try using a desktop email application, such as Outlook, Thunderbird, or Apple Mail. Email applications don't use your IP address as part of the authentication process, so a changing IP address isn't a problem.

"Authentication Failed"

An "Authentication Failed" error means the email server cannot verify that your email access is authorized. This is typically due to a mistyped password, but it can also be caused by incorrect username, connecting to the wrong server, or blacklisting. Follow these steps to resolve the issue:

  1. Reset your email password.
  2. Open your email application and check the following settings:
    1. Update the password to your new case-sensitive password.
    2. Confirm your username is the full email address, such as [email protected].
    3. Confirm the server name is where is your domain name.
  3. Does your email application work now? If not, here are a few tips:
    1. If you've recently changed where your domain points, or if you've upgraded or downgraded your hosting plan, wait up to 72 hours for your new DNS settings to propagate worldwide.
    2. It's also possible that your local IP is blacklisted. Wait 24 hours and try again, using webmail in the meantime. If it still doesn't work after 24 hours, check out local IP could be blacklisted.
    3. The local IP address your email application is using may be blacklisted, which can happen after a few too many failed login attempts within a short period. If you suspect this is the problem, try using another internet connection, such as a mobile data or a WiFi, and try again. Check out If Your Local IP Is Blacklisted for more information.

Certificate Name Mismatch

This error is a warning from your email application that the certificate for SSL that the server uses doesn't match the name that your email application was expecting. Variations of this error include:

  • Invalid Certificate
  • Mail can't verify the certificate for
  • The identity of cannot be verified.
  • The certificate for this server is invalid.
  • Host name mismatch
  • A secure connection cannot be established with the server.
  • The name on the security certificate is invalid or does not match the name of the site.
  • The server you are connected to is using a security certificate that cannot be verified.
  • This Connection is Untrusted. Confirm security exception.

If your email application is set up using Private (with SSL) settings, and you're using your domain name as the mail server (such as, your email application expects the SSL certificate to contain your domain name, when it contains the name of the Just Host server (such as instead. Because of this mismatch, your email application will warn you that the name on the Just Host server's certificate doesn't match your domain name. This is normal.

Email applications will allow you to continue to send and receive mail, but you may need to adjust a setting in your email application to confirm you're aware of this configuration. Each email application has slightly different steps for setup. If you aren't sure which setting to change, check out our Email Application Setup Guides.

"550 Sender Verify Failed"

This usually means the inbox you're sending to or from is full, or your mail routing setting in the zone editor is wrong.

  • Full mailbox. Mailbox storage quotas are set to 250MB by default, but some plans allow you to turn off the limit and set mailbox quotas to "unlimited." If an email account is at or past its capacity, sending out from it won't work and you'll get a "Sender Verify Failed" error. To check on the mailbox quota of an email account follow these steps:
    • Log in to your Just Host control panel.
    • Go to the Hosting menu and click Email in the submenu.
    • Locate the email address having problems in the list, and click view details button on the right to view detailed information about the email account.
    • Look for the mailbox quota. If the account is at or exceeding its quota, increase its limit or delete emails to save space.
  • Mail Routing. Your domain's email routing setting may be incorrect. Check out How to Modify MX Records: Email Routing for more information.
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