VBA Outlook SendUsingAccount returns Nothing - vba

Question

At our company, we use Outlook Exchange Desktop edition. Some of us have multiple accounts to send/receive emails from. I have created a VBA macro to check for each email when pressing the Send button what account they are sending the mail from, and then to create a handler that checks if this mail arrives in the "Sent items" folder. After arriving it takes this mail and saves it to a predefined folder.
At first I created this macro to only work with the default account and default folder for sent mail. It worked perfectly. Now I added some code to check the account it is sent from in the correct "Sent items" folder (the one of the correct account). Therefore I used the MailItem.SendUsingAccount property.
When applying this macro, 8 out of 10 times, I get the correct account and the macro works fine. The other 2 times, the SendUsingAccount property return "Null" or "Nothing" (I don't know the difference between these two). I found an other thread here where another user suggests the assignment of accounts to Mailitems is not always reliable, but it doesn't state a proper solution to my problem. Why do I sometimes get nothing as a returnvalue and other times it works perfectly fine? When it's not working, it's always about the code line: ZendAcc = Item.SendUsingAccount. Here the ZendAcc variable cannot store the empty SendUsingAccount return.
VBA:
Public WithEvents myOlItems As Outlook.Items
'Sub triggered when pressing the send button in outlook email
Private Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim ZendAcc As String
'Checking for multiple accounts
If Application.Session.Accounts.Count > 1 Then
'Check if the itemtype is MailItem. (normally it will always be correct)
If TypeName(Item) <> "MailItem" Then
MsgBox "There is no MailItem"
Exit Sub
Else
'Store AccountName in String
ZendAcc = Item.SendUsingAccount
If ZendAcc = "" Then
Exit Sub
End If
'Create the handler and give it the Accountname String
Call Initialize_handler(ZendAcc)
End If
Else
'When there is only one account, the Accountname doesn't matter, but you need a String
Call Initialize_handler("Useless")
End If
End Sub
Public Sub Initialize_handler(ByVal zendAccount As String)
Dim Store As Store
Dim Folder As Folder
'If there are multiple accounts, check for the right sent mails folder, otherwise use the default one.
If Application.Session.Accounts.Count > 1 Then
For Each oAccount In Application.Session.Accounts
If oAccount.SmtpAddress = zendAccount Then
Set Store = oAccount.DeliveryStore
Set acFolder = Store.GetDefaultFolder(olFolderSentMail)
Exit For
End If
Next
Set myOlItems = acFolder.Items
Else
Set myOlItems = Application.GetNamespace("MAPI").GetDefaultFolder(olFolderSentMail).Items
End If
End Sub
'Catch the added mail and save to folder
Private Sub myOlItems_ItemAdd(ByVal ObjectSent As Object)
'Code to do something with this mail. In my case: store to defined folder.
End Sub

Answer 1

If the account was explicitly set and the message has not been saved first, you might get null (aka Nothing in VB). In that case, assume the very first account from the Application.Session.Accounts collection will be used.