Outlook "sendusingaccount" property

[Migrated content. Thread originally posted on 09 September 2011]

Has anyone used the property SENDUSINGACCOUNT of Outlook to indicate the sender account?
It lets you choose a different account from the default account of your Outlook. This property appears in Outlook 2007.

Once I have found in my Outlook the account I want to use, I have it in my handle "olaccount".
Then I want to set this property:

modify olmail @sendusingaccount is olaccount

When I finally send my e-mail, the sender address is the default account, not the account I chose.
Can anyone help me? Thank you! :-)