did you agree to accept service? If so, they can be mailed to you or handed to you by anybody, including your spouse. You would have to sign the acknowledgment of service on the summons.
Otherwise the service does not appear to be valid. In MI it must be sent by certified or registered mail, by somebody other than the plaintiff, or served by any adult other than you.
You would not receive a decree unless you requested one or somebody requested one and sent it to you. It matters not if it was registered/certified or anything else as it is simply a copy of the courts order.
There is also a divorce certificate or an apostille available. Again, does not need to be certified/registered deliver. It is a record in the same way a birth certificate is a record. No need to have receipt verified.