I used St Brendans Isle for several years while living aboard and moving a lot. I found their service to be great. Traveling nurses and full-time RVers also use them. When we head out again next year, we plan to use them again.
Now they have an optional service where they'll scan the contents of your mail and email the images to you so you don't have to have the hard copies physically sent anywhere unless you want a hard copy.
They also provide assistance with obtaining and shipping replacement boat parts to you in far-flung parts of the planet, as well as with managing your yearly vessel documentation renewal (for U.S. documented vessels.)
When I originally signed up with them, I was living on my boat in California. They provided me with everything necessary to legally change my address and voter registration to Florida. Since then, I've actually had the opportunity to go by their location in Green Cove Springs, FL, a small town on the St. John's river.
I recommend them without reservation.
Can not recommend St. Brendan's enough.
We signed on with them in 2012. We made a physical trip to Green Cove Springs and picked up a driver's license and registered to vote all in one day. The DMV was fast and friendly and knew what we were about and had no problem issuing our license.
We did at one point receive an "address confirmation" from the voter registration people asking if we still lived there.
The bigger problem we've seen is places like banks, your typical customer service rep does not know the difference between a PMB and a P.O. Box, and the distinction is very important.
SBI gets you a PMB, a Private Mail Box. You set SBI as your Legal Mail Agent; they can sign for packages for you, sign and return your USCG documentation renewal, etc. Fedex and UPS deliver there too - it IS considered a legal street address.
We had some troubles opening an account with Fidelity because the CSR would not accept that SBI was not a P.O. Box. We finally got it, but only after I told them to delete all my accounts as I was going to find a company that was smart enough to figure out that they actually wanted my money...a supervisor got on the case and sorted it.
But I was right, they were in the wrong and I had to instruct them...a PMB is not a P.O. Box and that makes a BIG difference in your legal situation with SBI.