I grew up with an ex K9 WWII German Shephard dog in the home. Great dog but hated mailmen, must have been the uniforms? Dog died in 1956, 5 years later they still would not deliver mail to the home.
My dog hated the mailman *and* the UPS guy. Actually she wasn’t fond of anyone who just walked up to the house with impunity. Once you came inside however, she was your buddy.