Consider the following scenario:
You connect to a Microsoft Exchange Server 2010 mailbox by using Microsoft Office Outlook in online mode.
You add an additional POP3 account or an additional Internet Mail Access Protocol (IMAP) account in the same Outlook profile.
You create an email message that includes an attachment.
You select the POP3 account or you select the IMAP account as the sender, and try to send the email message.
In this scenario, the email message remains in the Outbox. Additionally, you receive the following error message:
Task '<the POP3 account or the IMAP account> - Sending' reported error (0X800CCC13): 'Unable to connect to the network. Check your network connection or modem.'
To resolve this issue, download and then install Exchange Server 2010 Service Pack 1 (SP1) from the following Microsoft website:
To work around this issue, access the mailbox by using Outlook in cached mode.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about email account types, visit the following Microsoft website: