The mailbox of the site enables you to communicate with your suppliers.
It is easy to know whether you have new mails. If you do, the MESSAGES icon in the navigation bar will change from grey to red:
Clicking on the red MESSAGES icon will bring you
directly to your INBOX.
Alternatively, you could access your INBOX via the ACCOUNT page and
click on

You will then be shown all mails that are in your
INBOX. Unopened mails will have this symbol:
,
opened ones will have this symbol: 
If you wish to reply to this mail, you can then
click on

If you want to delete it, you can click on

Enter some details about your customer (leaving
everything empty will list ALL your customers) and click on SUBMIT to
search for him/her:
Click on SENT ITEMS:

You will then be shown all mails that are in your SENT ITEMS tray.