best just not to open it. If they sent it to a blocked account your fine. If it was sent to an open account and you are goign to read it from a computer that you got blocked on, I'd avoid it for safety reasons; likewise if you are reading it from a blocked account on an open account computer. I personally never even log into my email unless I am on my stealth account. Mixing & Matching different accounts with computers is just asking for a mistake to be made through neglect.
Amazon e-mails look all text-like but I don't risk it. Think I might have opened one up once on an e-mail from a comp that's def blocked via IP, etc - account went down about 1 week later...can't say for sure whether it was for that or for listings but did get the linked to suspended account message.