I have neighbors blocking my mailbox with their cars. Where do I file a complaint? Also a portion of there fence is down. Which is shared between property. What can I do to get them to fix the fence

Not sure about the parking in front of the mailbox since it is a public street but for the fence call 311 and be sure to specify that even though you all share the fence it's there portion. Otherwise you both can be held responsible for it.

Call Your neighbor Post office and make a complaint, also try to find the U.S title Code for delay mail, and make a complaint with your sub Court House....