Complaining on Facebook / Nextdoor may make you feel better, but it won’t help the problem. Instead of logging in to social media go the USPS website: https://emailus.usps.com/s/personnel-inquiry and fill out the form.

• Who is this issue about: Letter carrier
• Do you know the name: No
• I have a: Complaint
• Details: Rude/Unprofessional
• Additional Information: This is where you describe the issue, delivered to wrong house, gave lockbox key for wrong locker, left community mailboxes open, etc.
• Date of incident or best guess: Get as close as you can
• Time: leave blank
• Where did incident occur: Other Location
• Street, City, State, Zip: Put in your address, even though it took place at the mailboxes.
• Contact Information: Fill in as desired.

Other ways to contact the post office (though not as effective from my experience)

USPS
5608 State Road 674
Wimauma, FL 33598
(813) 634-4282

USPS Consumer Affairs
PO Box 39756
Tampa, FL 33630
1-800-ASK-USPS

USPS Office of the Consumer Advocate
475 L’ Enfant Plaza SW
Washington, DC 20260

USPS Office of Inspector General
1-888-877-7644