I have not seen your code so I cannot explain why your code was causing a slowdown of your system. It is common to use late binding and to use variables that are larger (require a lot of memory) than they need to be.
When possible, you want to use the New keyword in your declarations. Also, you want to explicitly declare the type. When you choose a type, your choice should be one that best fits the situation. You do not want everything to be Object when you need Application or MailItem.
In short, Access does not have to guess what type to use and this is where the optimization occurs.
Code:
'Reference Microsoft Outlook and
'use early binding
Dim objOutlook As New Outlook.Application
Dim objNewEmail As MailItem
Dim objAttachReport As Attachments
'Instantiate your objects
Set objNewEmail = objOutlook.CreateItem(olMailItem)
Set objAttachReport = objNewEmail.Attachments