Is it possible to download and assign an email to the leads even if the email has already been downloaded and read by another application?

For example, I have setup my thunderbird to read the email from sales@company.com and also configured openerp to receive and create a lead from sales@company.com.

So, when i get an email to sales@company.com and if i first open it with thunderbird i am not getting it in the openerp leads but if i get it in openerp first i am able to receive it in my thunderbird also.

Is this possible? I have setup the email using IMAP on both the places