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 June 24, 2019 Luis Alvarez / Getty Images MS Office Outlook Word Excel Powerpoint Tweet Share Email Is your Outbox growing faster than your Inbox? Does Outlook Express make you despair with error messages like "Message could not be opened from Outbox folder." or "Some errors occurred while processing the requested tasks."? Does Outlook Express send multiple copies of outgoing messages? There are a number of configuration missteps (such as a port change enforced by the email provider that wasn't communicated to you) and Outlook Express problems (like a corrupted Outbox folder) that can halt your outgoing mail. Identify and Fix Problems Sending Mail in Outlook Express Fortunately, there's more than one thing you can try to remedy the situation and finally start sending mail again: Check your outgoing mail server settings Navigate to Tools > Accounts... from the menu. Highlight the desired account and click 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 checked 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 things, such as one for all mail sent out over the course of a year. Make sure you compact folders manually after moving messages. Rename a Corrupt "Outbox.dbx" File With Outlook Express closed, open your Outlook Express store folder in Windows Explorer and rename the Outbox.dbx file to Outlook.old. Note that you can no longer 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 helps, you can have Outlook Express create an SMTP log file to find out more about what's going on behind the scenes.