A suspended bounce indicates the address has bounced before as non-existent. When an address bounces for the first time it will show as non-existent and behind the scenes will be quarantined for 15 days. Once this time period is up we will try to send to this address again once and if it bounces again as non-existent it will show as suspended for the future. Please note, this applies to all Constant Contact accounts so if you send to an address for the first time and it bounces as suspended it's likely that it bounced as non-existent from another Constant Contact account.
Hope this helps,