Error 501:  Invalid Domain Name or Address

The infamous "501 Errors" can result from several different problems, most of which are listed below.  Common error messages include: (i) An unknown error has occurred. Account: <acct>, Server: <srv>, Protocol: SMTP, Server Response: '501 Invalid domain name', Port: 25 Secure(SSL): No, Server Error: 501, Error Number: 0x800CCC63; (ii) An unknown error has occurred. Account: 'MSN Mail', Server: 'smtp.email.msn.com', Protocol: 'SMTP', Port: 25, Secure(SSL): No, Server Response: '501 Invalid Address', Server Error: 501; or (iii) An Unknown error has occurred: 501 Invalid Address.  Listed in order of priority from the most frequent to the least frequent, the potential solutions to this problem are set forth below.

• Computer Name Too Complex or contains invalid characters   The most common problem is that your computer name is too complex.  Your "Computer Name" identifies your computer (just as if you were on a local network) and gets sent to the mail server when you dial in. Any nonstandard characters in the Computer Name can cause problems. It should be letters and numbers only, e.g., no @ sign, no extended international characters, no slashes, no periods, etc. It also should not include the name of your mail server, which can confuse things even more. Something simple like your name, e.g., EMiller, is best.   To eliminate this possibility, follow these steps:
  1. Click Start, point to Settings, and then click Control Panel.
  2. Double-click Network, and then click the Identification tab.
  3. Change the computer name in the Computer Name box so that it contains only any combination of letters (A-Z) and numbers (0-9). Do not use non-alphanumeric characters or blank spaces.
  4. Click OK.
  5. Restart Windows when you are prompted.

  OR dial up users should follow this link.

• DNS Name Contains Invalid Characters   Another common cause of the 501 Error is  is that the Domain Name Service (DNS) host name or the DNS domain name specified in the Transmission Control Protocol/Internet Protocol (TCP/IP) properties contains invalid characters.  As a precautionary note, it's normally best to leave this blank ("disable DNS"), and put all the relevant information in the specific connectoid you use to dial up. Many ISPs recommend putting this information in the Network applet, which works fine if you're only using one dial-up connectoid. However, it opens up some potential for conflict that is better avoided. Letting the connectoid handle it is a little cleaner.   Despite that advisory note, to eliminate this issue as a possibility, verify that the DNS host name and the DNS domain name contain only valid characters. Valid characters for the DNS host name and the DNS domain name are letters (A-Z), numerals (0-9), and the hyphen (-). The period (.) is also a valid character when it is used as a separator, e.g., ab12-3.com.  To verify that the DNS host name and the DNS domain name contain only valid characters, follow these steps:
  1. Click Start, point to Settings, click Control Panel, and then double- click Network.
  2. On the Configuration tab, click TCP/IP, and then click Properties.
  3. Click the DNS Configuration tab.
  4. In the Host box, verify that the name contains only valid characters.
  5. In the Domain box, verify that the name contains only valid characters.
  6. Click OK, click OK again, and then click Yes if you are prompted to restart the computer.
• Sender's Email Address Incorrect   The 501 Error will result if your email address has any inadvertent spaces in it.  To double check this, go to Options -> Program Settings and check the "Your Email Address" field.  If you find that your email address has extra spaces in it, eliminate those spaces.
• Recipient's Email Address Incorrect   The 501 Error can result if the email address in the To: field is incorrect.  Verify that the e-mail address specified on the To: line is typed in the correct format. Make sure there are no spaces or extra or missing periods in the e-mail address.
• Network Client Not Installed  Yet another cause (particularly with MSN) is that Client for Microsoft Networks is not installed.  To eliminate this as a possibility, go to Start | Settings Control Panel and double- click on the icon for the Network applet (you can also do this by highlighting Network Neighborhood on the Desktop, right clicking and selecting Desktop) . On the Configuration tab, verify that Client For Microsoft Networks is listed in the "The following network components are installed" box. If Client for Microsoft Networks does not appear, add the Microsoft Client for Microsoft Networks by using the following steps:
  1. a. Click Add, click Client, and then click Add
  2. In the Manufacturers box, click Microsoft.
  3. In the Network Clients box, click Client for Microsoft Networks  and then click OK
  4. When prompted to restart your computer, do so.
• SMTP Server Problems   There is a problem with your ISP's SMTP (Simple Mail Transport Protocol) server. This is the server that is used for outgoing mail.  To determine if there is a problem with your ISP's SMTP server, wait for a period of time, and then try to send the message again. If you still receive the error message, contact your ISP.
• Other   The message header may be damaged.

Quick Links