The Mail House pub in Staple Hill received the postcard in which the sender said they were very disappointed the pub did not ‘seem to care much about the vulnerable people’ in the society.
The pub had started hosting live music again after opening last month for the first time since lockdown.
The postcard, from an anonymous sender, bore a Guernsey postage stamp.
On one side was a picture of the Channel Island – and on the other an angry note.
‘Your music is played way too loud and you let your patrons sing along,’ the sender wrote.
‘This is not permitted and will accelerate the spread of the virus.
‘You also have no licence to play music outdoors. I have reported my concerns to the council.’
South Gloucestershire Council was investigating the complaint and was reportedly working with police on the matter.
What is still unknown is the Guernsey connection.
After the postcard was sent, the landlady called off one of the gigs which had been scheduled for last Saturday.
This sparked outrage on social media as Staple Hill residents criticised the ‘spiteful’ and ‘sad’ postcard.
Now the council has given the go-ahead for live music to resume at the pub but with some restrictions: only solo performers, not bands; 12 customers allowed in the beer garden at any one time; and no dancing.
Landlady Brenda Long told BristolLive that she had no hard feelings about the postcard, but wished the sender might have spoken to her.