Setting Outlook's Default mailbox programaticaly C# Microsoft Outlook Library 14.0

Question

I want to set the user selected domain(from list of domains configured in Outlook) from my application
as Outlook's Default mailbox programaticaly. Is there any function in outlook library 14.0 to set default mailbox from all configured outlook accounts ?
I am using C# and Microsoft Outlook Library 14.0 for Outlook 2010 for my application.

Answer 1

Hello Sridhar,
The Outlook object model doesn't provide anything for setting the default account in Outlook. These settings are stored in the windows registry. The How
do I get Outlook to actually default new emails to a specific account and not ignore the default setting? forum thread states the following:
Out of the box, Outlook 2010 SP1 and Outlook 2013 use the default account for Send to commands but not for new messages created while viewing a pst file (when a POP account is assigned to the pst file), unless you set a registry value to always force the use
of the default account.
To force all new messages to use the default email account, regardless of which pst file you are viewing, browse to the following registry subkey in Outlook 2010 and add a DWORD named NewItemsUseDefaultSendingAccount:
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Options\Mail
DWORD value: NewItemsUseDefaultSendingAccount
Value: 1
In Outlook 2013, the key is:
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Options\Mail
DWORD value: NewItemsUseDefaultSendingAccount
Value: 1
Registry key to force account selection every time
This fix is simple, but can get annoying, fast, since it forces the user to select an account every time they send a new message. (Replies and Forwards always use the account the message arrived on.)
This might be good for people who use multiple accounts and frequently (accidentally) send using the wrong account, especially if they are sending sensitive documents, as it will almost eliminate accidentally sending email from the wrong account.
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\outlook\options
Value Name: ForceAccountSelection
Value type: REG_DWORD: 1 for force, 0 to disable.
In Outlook 2013, the registry key is:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\outlook\options
Value Name: ForceAccountSelection
Value type: REG_DWORD: 1 for force, 0 to disable.
Also see Outlook 2010 does not honor the default sending account .
You may also find the
SendUsingAccount property of the MailItem class which allows to set an Account object
that represents the account under which the MailItem is
to be sent. For example:
Sub SendUsingAccount()
Dim oAccount As Outlook.account
For Each oAccount In Application.Session.Accounts
If oAccount.AccountType = olPop3 Then
Dim oMail As Outlook.MailItem
Set oMail = Application.CreateItem(olMailItem)
oMail.Subject = "Sent using POP3 Account"
oMail.Recipients.Add ("[email protected]")
oMail.Recipients.ResolveAll
oMail.SendUsingAccount = oAccount
oMail.Send
End If
Next
End Sub