3 choices. The first is the 30-day email holding period. The second is to temporarily forward the emails to your friends or relatives' addresses, and you can spend tens of dollars to forward the valid time to one year. The third is to call their supervisors every 30 days and ask to continue holding the mail. For special reasons it is also possible to have your friends collect all mail every 30 days. Do not keep mail in the mailbox until it is full, after 10 days all mail will be returned to the sender if unclaimed.
If you make an account on USPS.com you can manage getting a hold put on your mail. I can't remember the specifics of making the account, it was a while ago for me, but it's not too difficult, I believe.
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