We found a way long ago to eliminate the vast majority of junk mail. We use a PO Box. None of those grocery and other store packs of junk are placed in PO Boxes.
Now, mail while traveling. First, we get very little legitimate mail. We do everything online. So, no bills. No bank statements. No income tax forms. There is very little mail that we care about. We don't use mail. We'd be fine if there was no mail. Then what little is left we have processed just like St. Brendan's does, have any we care about scanned, and read it electronically.
Someone asked the question recently regarding GA. Well, there are mail receiving and forwarding services around the country, some nationwide services. Some don't have the residency assistance and other features of St. Brendan's but many have mail handling including opening and scanning if you choose.
St. Brendan's distinct advantages beyond mail forwarding are that Florida has no state income tax, no property tax on boats, and allows you to be a resident while "residing" at St. Brendan's. They accept a mail service as a physical address. Each state is different in that regard. Florida is easy to establish residency in.
A couple of nationwide services:
Plus several services in TX and FL, one in Oregon, and I'm sure many in other states.