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Microsoft Outlook: Email Stuck in Outbox

There are a number of causes of this problem.

Outlook 2003/2007 Settings

  • If email will not send or receive without manually pressing F9 or clicking Send/Receive, this may be because this has been disabled. Check that ToolsSend/ReceiveSend/Receive SettingsDisable Scheduled Send/Receive is not ticked.

  • Check that ToolsOptionsMail SetupSend Immediately When Connected is enabled.

  • Under ToolsOptionsMail SetupSend/Receive, check that each mail account has Send Mail Items enabled.

Connection Is Being Refused

  • Check the SMTP host is correct for your network. Many users outside a corporate environment send email via their ISP's SMTP (‘simple mail transfer protocol’) host. However generally ISPes only allow email to be routed via their mail servers from users connected to their network. For example, if you are an Internode customer you would use but if your machine is currently connected to, say, a network using Bigpond, or a wireless hotspot, Internode will refuse the connection. In this case you will need to alter your SMTP settings to be appropriate for the network you're on, or use an SMTP service will allows connections from anywhere (such as Internode's Securemail service or Netregistry's authenticated SMTP service.

  • Too many recipients. Some ISPs have restrictions on the number of messages you can send in a given period, or the number of recipients per message. It may be necessary to send messages with fewer recipients, or to wait for a while before sending. However, the message may not be being refused, but timing-out due to throttling occurring at the ISP's mail host. Increasing the server time-out threshold in the email client may allow the messages to be sent.

  • Spam blocked. Your ISP may be refusing messages from your IP address if it thinks you have been sending too many emails, or emails which identify as spam. Contact your ISP to resolve.

Outlook Cannot Communicate with the SMTP Server

  • Check for ISP outages. Many communications problems are upstream and resolve themselves eventually. Check your ISP's outage advisory page before embarking on other troubleshooting.

  • Check the SMTP host name. Sometimes ISPs change their hostnames, or retire old SMTP hosts.

  • Check the reply address. If the reply address contains a non-existent domain name, or an expired name, or one in which the domain records are invalid, some SMTP hosts will not accept the messages. A domain which is otherwise valid may also be refused if the hosting provider has put a block on it for spam violations (such as when a website has been infected or an email account compromised). The block has the effect the domain's MX record does not resolve and won't be accepted by upstream SMTP hosts. (An associated error might be “An SMTP protocol error occurred” or 0x800CCC78.)

  • Disable Secure SMTP. Some ISPs provide a “secure” SMTP service for outbound email. This encrypts the transport of the messages using SSL. Normal SMTP is not encrypted or authenticated. Secure SMTP is useful for unsafe/uncontrolled environments such as wireless hotspots, hotels and third-party LANs, and is also useful when not connected to your main ISP and a local SMTP provider is not available. But it is more complex and may be problematic for a number of reasons. (0x800CCC0E)

  • Check Internet Explorer settings. Windows Live Mail may report error 0x800CCC0D if Internet Explorer is set to Work Offline (see Windows Live Mail).

  • Check the router multiplexing is correct. If using PPPoE, the multiplexing must be LLC. If using PPPoA, it must be VC.

  • Try a different encapsulation. If your router is using PPPoE, switch to PPPoA, or vice-versa. PPPoA is generally preferable, but some (older) routers work best with certain ISP equipment one way or the other.

  • Lower the MTU in the router. Due to ISP hardware and software changes, a Maximum Transmission Unit (MTU) value which worked one day may be problematic the next. Lower it progressively until a value allows Outlook to communicate properly. Note that Outlook as opposed to Outlook Express seems to be more sensitive to MTU issues.

    ISP references: Bigpond.

The Message Is Sent Repeatedly

If the email is being sent successfully, but cannot be moved into the Sent Items folder, the message will be repeatedly sent and the recipient will receive multiple copies.

  • Disable outgoing virus scanning. Email virus scanners may timeout on large messages and silently fail, causing Outlook to assume the send did not work and keep the message in the Outbox. Scanning outbound email for viruses is a waste of time anyway, as modern viruses use their own internal SMTP engines to email themselves, and do not use the local email client.

  • Check the email store is less than 2Gb. Outlook personal folder files (.PST) on older versions of Outlook have a limit of 2Gb per file. As your email store approaches this, operations such as moving messages between folders stop working.

Software Update Required

Other Software Problems

  • Outlook 2007. When composing a new message in Outlook 2007, you can choose a different folder to save the message in (instead of Sent Items) under the Options tab. Outlook stores a list of previously-chosen locations. If you choose a location which no longer exists, then choose an existing location using the Other Folder... option, the message will simply be saved in the Outbox and not sent. Copy the contents of the message and send again. Delete the version stuck in the Outbox.

  • Outlook 2013. Messages may stick in the Outbox and display a network error (0x800CCC13 Cannot connect to the network). After closing and re-opening Outlook, the messages send, but subsequent messages become stuck again. This may occur if the KB2880470 or KB2863911 updates are installed, and Office 2013 was installed with the MSI installer (as opposed to the so-called Click-to-Run installer). Uninstall the update via Programs and Features. If the update reappears in Windows Update, hide it.

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