The shocking incident took place in Bury, Greater Manchester, on Thursday and left the owner of the house ‘disgusted’ after they reviewed the Ring doorbell footage.
They confirmed an investigation has been launched and branded the act ‘completely unacceptable’.
Footage shows the postie on his round before making his way up a garden path, clutching letters in his right hand.
The clip then shows him putting his right index finger over one of his nostrils as he reaches the front door.
He then appears to loudly exhale through his other nostril.
The homeowner said: “I was disgusted, especially with a pandemic but it’s disgusting to do it anyway.
“I rang my son straight away.”
The footage has been seen by Royal Mail bosses.
A spokesman said the incident was ‘completely unacceptable’ and that an investigation had been launched.
A statement read: “Royal Mail expects the highest standards of behaviour from our people while out on deliveries and collections.
“This behaviour is completely unacceptable and we apologise to our customer.
“We are investigating this incident.”