If you use Outlook and have been running into the problem of sending emails, such as it goes into the outbox and just sits there.

To get it to "leave the premises," you have to open up the Outbox folder and click Send again. From what I seen and heard this is a rather common problem and can have several different causes. Here are some things to try if your “sent mail” is getting stuck in the outbox (depending on the version of Outlook you're using, these may vary):

1. In Outlook, click Tools > Options > Mail Setup. Check "Send immediately when connected."

2. Click on the Send/Receive button on the Mail Setup General tab. Make sure both options to "Include this group in Send/Receive" are checked. Make sure that your account is included in the Group to send.

3. Try registering a library file that's used in the send/receive process. Click Start > Run and type regsvr32 inetcomm.dll

4. Check to see whether an antivirus email check is slowing down the sending and receiving process. Try disabling AV and sending to determine whether this is the problem. Check to determine whether other programs running in the background are interfering. Disable them one at a time. This includes the firewall, antispyware, antispam, and all anti-malware programs.

5. In the account settings, Advanced settings, change the server timeout time from 1 min to 5 min.

6. Check to see whether outgoing mail server authentication is required. Try selecting that option in account settings and use same setting for the incoming server.

7. If all else fails, create a new Outlook profile. Here are some tips on doing that:

Source: Windows7News