It looks like you are interested in 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. The SendUsingAccount property can be used to specify the account that should be used to send the MailItem when the Send method is called. 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
Be aware, Microsoft does not currently recommend, and does not support, Automation of Microsoft Office applications from any unattended, non-interactive client application or component (including ASP, ASP.NET, DCOM, and NT Services), because Office may exhibit unstable behavior and/or deadlock when Office is run in this environment.
If you are building a solution that runs in a server-side context, you should try to use components that have been made safe for unattended execution. Or, you should try to find alternatives that allow at least part of the code to run client-side. If you use an Office application from a server-side solution, the application will lack many of the necessary capabilities to run successfully. Additionally, you will be taking risks with the stability of your overall solution. See Considerations for server-side Automation of Office for more information.