Software & Apps MS Office Troubleshooting Outlook Express Mail Sending Problems What to do when you can't send mail with Outlook Express by Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated on April 19, 2020 Luis Alvarez / Getty Images MS Office Outlook Word Excel Powerpoint Tweet Share Email There are a number of configuration missteps (such as a port change enforced by the email provider that they did not communicate to you) as well as Outlook Express problems (such as a corrupted Outbox folder) that can halt your outgoing mail. Fortunately, there's more than one thing you can try to remedy the situation and finally start sending mail again. Outlook Express was a free email program that shipped with early versions of Windows. Microsoft no longer offers support for the application. Check Your Outgoing Mail Server Settings To identify and fix problems sending mail in Outlook Express, begin by making sure you have the correct settings enabled. Navigate to Tools > Accounts from the menu. Highlight the desired account and choose Properties. Make sure the correct server name is entered under Outgoing mail (SMTP) on the Servers tab. On the same tab, verify My server requires authentication is selected if needed (which is typically the case). Under Settings, you can specify a username and password different from your incoming mail credentials. On the Advanced tab, make sure This server requires a secure connection (SSL) is checked under Outgoing mail (SMTP) if your outgoing mail connection must be encrypted. Check the port under Outgoing mail (SMTP) too. Typical ports include 25 and 465. Make Sure Your "Sent Items" Folder Isn't Too Large The folder can hold 2 GB at most. To check the size, go into your Outlook Express store folder and examine the Sent Items.dbx file size. Move messages from the Sent Items folder in Outlook Express to another folder. Make separate folders for separate items, such as one for all mail sent out over the course of a specific year. Make sure you compact folders manually after moving messages. Rename a Corrupt "Outbox.dbx" File Renaming this file creates a new one, which could resolve an issue with a damaged file. With Outlook Express closed, open your Outlook Express store folder in Windows Explorer and rename the Outbox.dbx file to Outlook.old. You will no longer be able to access any messages in your "old" Outbox folder. If the renaming has fixed your delivery problems, you can delete the Outbox.old file. If nothing else helps, you can have Outlook Express create an SMTP log file to find out more about what's going on behind the scenes.