Article ID : S500028175 / Last Modified : 11/04/2018

While sending a mail with Outlook Express Ver. 5.0, an error message appears and the transmission of the mail fails sometimes. Why is this so?

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When I try to send a mail with Outlook Express Ver. 5.0, the following message appears and the transmission of the mail fails sometimes. Why is this so?

--Error message--
Host is not found. Check if the server name is correct.
Account: : Server: : Protocol: SMTP, Port: 25, Security (SSL): None, Socket error:

To resolve the symptom, please refer to the following procedures to check the relevant settings:.

--Settings of connection--
1) Start [Outlook Express]. Vacate the [Outbox] folder by deleting or moving the undelivered mails remaining in it.

2) Click [Accounts] from the [Tools] menu to display the [Internet Accounts] dialog box.

3) Click the [Mail] tab in the [Internet Accounts] dialog box, and then click from the account list the account you used when the error message appeared. Then, click the [Properties] button.

* As a form of precaution, we would suggest that you to back up the account in advance. For further details, please refer to the relevant solution below.

4) Click the [Connection] tab in the [(Account name) Properties] dialog box to check the type of connection.

- If connected to the Internet via LAN,
Select the [Always connect to this account using] check box and select [Local Area Network (LAN)].
- If connected to the Internet through dial-up connection,
Clear the [Always connect to this account using] check box.

5) After changing the settings, click the [OK] button, and then click the [Close] button in the [Internet Accounts] dialog box.

* If you are unable to send a mail normally when connection is made to the Internet via LAN, and [Local Area Network (LAN)] is selected, please check with your network administrator if the network settings have been correctly established.

6) If you are unable to send a mail normally even after carrying out step 4 in the environment where the machine is connected to the Internet via LAN, please check with your network administrator if the network settings are correct.
If the network settings are correctly established, please check the settings of your mail server.
If your machine is connected to the Internet via dial-up connection, please refer to step 7 to establish dial-up connection manually.

7a) Double-click the [My Computer] icon on the desktop, and then double-click the [Dial-Up Networking] icon.
7b) Double-click the connection icon of your service provider to display the [Connect To] dialog box.
7c) Enter the data into the [User Name], [Password] and [Phone number] text boxes, and click the [Connect] button.

* If you are unable to establish a dial-up connection after performing the step above, create a new dial-up network connection to connect your machine to the provider and check if you can establish a connection.

8) Create a new mail addressed to your own mail address and click [Send]. If the mail is sent normally, the appropriate dial-up connection may not be specified in the pull-down menu under the [Always connect to this account using] check box in the [(Account name) Properties] dialog box.

If the error message appears and the mail is not sent even though the settings of connection is properly made (you can browse Web pages through the connection to the Internet), please refer to "--Settings of your mail server--"

If you are unable to connect your machine to the Internet normally, please refer to the same solution mentioned above as well.

--Settings of your mail server--
You may check the settings of your outgoing mail (SMTP) server with the procedure below:

1) Start [Outlook Express]. Vacate the [Outbox] folder by deleting or moving the undelivered mails remaining in it.

2) Click [Accounts] from the [Tools] menu to display the [Internet Accounts] dialog box.

3) Click the [Mail] tab in the [Internet Accounts] dialog box and click the account that displayed the error message from the account list. Then click the [Properties] button.

* As a form of precaution, we would suggest that you to back up the account in advance. For further details, please refer to the relevant solution below.

--Back up the set account information--
4) Click the [Servers] tab in the [(Account name) Properties] dialog box to see if the correct mail server name is entered into the [Outgoing mail (SMTP)] text box.
* To obtain information on the server name, please contact your service provider.

5) Click the [Advanced] tab in the [(Account name) Properties] dialog box and check if the proper port number is assigned to the text box located on the right side of [Outgoing mail (SMTP)] of [Server Port Numbers]. As a standard, 25 is assigned to [Outgoing mail (SMTP)] but the port number used for the connection to the mail server to send/receive mails varies depending on providers. To obtain the correct port number, please contact your service provider.

6) Click [OK] and then click [Close] in the [Internet Account] dialog box.

7) Exit [Outlook Express].

8) Connect your machine to the Internet manually and start [Outlook Express].

9) Create a new mail addressed to your own mail address and click the [Send] button.

If an error message appears and the mail cannot be sent even after executing the steps above, delete the account information where the symptom occurs and create a new account again.