Whenever I send an email using Outlook 2003, a message appears saying the email could not be sent, and the message remains unsent in the Outbox. This issue occurs irrespective of the message size, or any attachments. Most annoying is the problem is only intermittent - sometimes when I send a message, Outlook says the message was not sent (and remains in the Outbox) but I find the message has actually been sent and received by the intended recipient! A possible related issue is I cannot simply delete these unsent messages from the Outbox - I have to drag the messages into Deleted Items folder. These problems are causing major grief, as I have no idea whether the emails I have been sending are actually being sent. The computer is running Windows XP Professional SP2 with PC Cillin (Trend) AV 2006 (which is configured not to scan outgoing mail).

Given the symptoms of the issue, in particular as you cannot delete emails the normal way from the Outbox (but have to drag them to Deleted Items), combined with the fact the problem is intermittent, the issue is indicative of a problem with Outlook itself. I found an article on Microsoft Knowledge Base (support.microsoft.com/kb/195922) which deals with the issue of messages being stuck in the Outbox when using Outlook 2000. The procedures in the article could be useful at resolving your issue, so I have based my suggested solution(s) on these procedures, but adapted them for Outlook 2003.

We should always deal with the simplest causes before going to more complex causes. First, make sure Outlook is not in offline mode. In offline mode, Outlook does not send any messages but instead holds the messages in the Outbox until Outlook goes into online mode, allowing the messages to be sent. To check, go to the ‘File’ menu and check whether ‘Work Offline’ is ticked. If so, click the option to turn-off work offline.

Should Outlook not be in offline mode, the next possible cause of this behaviour is the Outlook PST file is corrupt. The Outlook PST file is where Outlook stores all user data, including email messages. If the PST file is damaged, this could cause problems moving messages between folders (and possibly problems when sending messages). There is a handy utility included with Outlook called SCANPST.EXE which can be used to scan and repair any detected damage in PST files. Before using this utility, delete any waiting messages from your Outlook Outbox and close Outlook (to give the utility exclusive access to the PST file). The location of this utility varies, so you will need to search your hard drive for this file. Go to the ‘Start’ menu > ‘Search’ and search for the file ‘SCANPST.EXE’ (without the quotes). Once the utility is found, double-click on the file to open the utility. You will need to specify the location of your Outlook PST file. To find the location of this file, go into Outlook then click the ‘File’ menu > ‘Data File Management’. You should see a list of the PST files. Record the location of your Personal Folders file (you may need to highlight the entry and click the ‘Settings’ button to read the full path to the file). Once you have determined the path to the PST file, specify the location of this file in the SCANPST.EXE utility. Be aware: the PST file is likely to be in a hidden directory, so you may need to enable the viewing of hidden files and folders (by opening Windows Explorer, then going to the ‘Tools’ menu > ‘Folder Options’ click the ‘View’ tab and enable ‘Show hidden files and folders’). Once the PST file is specified, click ‘Start’ to begin scanning the PST file. Once the scan has completed, start Outlook and delete all the waiting messages from your Outbox. Then, create and attempt to send a new message to see whether the problem has been resolved.

If running the SCANPST utility does not resolve the issue, there is a possibility the PST file is still somehow corrupt. In this case, you could try creating a new PST file to see whether the problem is resolved. Go to the ‘File’ menu > ‘New’ > ‘Outlook Data File’. In the list of storage types, select ‘Office Outlook Personal Folders File (.pst)’ and click OK. You will be asked to save the PST file. You should be able to accept the default file name, although you may wish to name the file as something like ‘Personal Folders New.pst’ to help identify this file from others. Click ‘OK’. Finally, the properties for the new PST file will appear. Give the new PST file the name ‘Personal Folders New’ and click OK. You will see the new mail folder ‘Personal Folders New’ appear in the Outlook window. We now need to set your mail accounts to use this new PST file. Go to the ‘Tools’ menu > ‘Email Accounts’. Select ‘View or change existing e-mail accounts’ and click ‘Next’. Select your email account and under ‘Deliver new e-mail to the following location’ select ‘Personal Folders New’ then click ‘Finish’. A message will appear to confirm the change, so click OK to accept the change. You will notice the ‘Personal Folders New’ folder now has the standard mail sub-folders (e.g. Inbox, Outbox, etc.). Restart Outlook and then try sending an email message. Should this work correctly, the new PST file seems to have fixed the issue. In which case, copy your email across to the new PST file (excluding the Outbox) and continue using this new file. You can copy the mail across by selecting and dragging the mail from the folders under the old PST file, to the folders under the new PST file.

Should this not work, go back to using the original PST file. You will also need to set Outlook to use the old PST file for mail, which can be done through the ‘Email Accounts’ option. Also, new email may have downloaded into the new PST file’s mailbox. In which case, you will need to copy this new mail back into your old PST file (so all your email is in the one place).

Finally, if the problem is still not resolved you can try working through the other procedures included in the Knowledge Base article (such as having an incompatible add-in with Outlook). If you are able to resolve the issue please let me know, as I would be interested in hearing the cause of the issue.