This was 15 years ago, but I headed from Denver to Sofia, Bulgaria on British Airways, with a plane change in London. I thought I was clever, coming back home with about 2 weeks left on my passport, thinking I was squeezing about every possible day out of it! The BA check-in agent in Denver said nothing, letting me on the plane to London, with no indication something would be wrong. After an overnight stay at the Holiday Inn close to Heathrow, I headed to the terminal to check in for my flight to Bulgaria. That’s where they wouldn’t let me on the plane, because I didn’t have a 3-month window left on the passport. The next flight to Sofia was in 4 days, and so I had an unexpected 4 day vacation in England, part of which was spent scrambling to get a new passport issued at the American Embassy in London. If you have the time before your Iceland trip to get a passport renewal to be safe, the peace of mind sounds like it would be worth renewing now.
As for your mail issues, check with your local Postmaster. They should check with their USPS District Address Management Systems (AMS) office to ensure that they accurately have your old and new addresses correctly listed in their address database, and with the District Computerized Forwarding System (CFS) office to ensure they have your mail-forwarding orders correctly reflected. That should ensure that your mail is all forwarded to the current mailing address.
