a lot of email sounds (sent mail, incoming) are audible when I wake up my Air (10.8)

Strangeness: when I wake up my air it occasionally sends off a string of email swoosh sounds (sent mail) and dings (arrival sounds of mail): like 20 in succession. Is it syncing with the cloud (my iPad)? I can't figure out why this happens. No visible new mail in or out in my apple mail boxes.

Tx