Just Host Web Hosting Help

Understanding Email Error Messages

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 john@example.com.
    3. Confirm the server name is mail.example.com where example.com 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 example.com
  • The identity of mail.example.com 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 mail.example.com), your email application expects the SSL certificate to contain your domain name, when it contains the name of the Just Host server (such as box123.Justhost.com) 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.
Knowledgebase Article 18,493 views bookmark tags:


Was this resource helpful?

Did this resolve your issue?


Please add any other comments or suggestions about this content:





Recommended Help Content

Why do my email messages keep getting returned?
Knowledgebase Article 210,626 views tags: email messages returned sending

. Click the SquirrelMail logo. This takes you to the main interface screen for SquirrelMail. Click 'INBOX' from the folders on the left. Now, you can read the emails you've received. Here is the place
Getting Started Article 165,687 views tags: email message send squirrelmail subject

Understanding Internet email headers.
Knowledgebase Article 131,748 views tags: email header ip

Related Help Content

Email is not being received when forwarded to free email services such as Gmail, Yahoo, or Hotmail and other ISP's that provide email service such as AOL, Comcast, Cox, etc. It can show completed in t
Knowledgebase Article 137,385 views tags: email forward

How to restore Email Messages the Site Backup Pro tool
Knowledgebase Article 103,050 views tags: backup email forwarders restore site

. Click the RoundCube logo. This takes you to the main interface screen for RoundCube where your Inbox will be displayed. On the left are your email folders, by default, RoundCube will always show you
Getting Started Article 183,411 views tags: email message reply roundcube send

Occasionally SSL Certificates are reissued and this causes email clients to prompt users to take action after the certificate is changed.
Knowledgebase Article 19,244 views tags: email security

POP POP, also known as POP3, is an E-mail protocol that is used when people wish to have a copy of their E-mail messages, along with any attachments, to be downloaded to their computer for viewing. D
Getting Started Article 168,225 views tags: email

A helpful overview of Horde Groupware
Getting Started Article 128,820 views tags: email icon message select send

If you find some of your emails end up your recipients Spam folder, arrive late, or sometimes don't arrive at all, this article can help you improve the deliverability of the messages you are sending.
Knowledgebase Article 107,322 views tags: delivery email filters receiving sending working

Why Am I Getting Duplicate Messages in Outlook 2002?
Knowledgebase Article 141,585 views tags: duplicate email outlook