A new post box will be installed near the West Bromwich Post Office in New Square Shopping Centre.
The move follows the intervention from local MP Tom Watson.
A 400 signature petition was presented to Mr Watson in October and he immediately opened up discussions with the chief executive of Royal Mail, Moya Greene.
Tom Watson MP said:
"Royal Mail refused to install a new post box outside of the West Bromwich Post Office but the decision made absolutely no sense, which is why residents started the petition.
"We have a brand new Post Office in New Square. I see many people queuing up for stamps in order to send cards and letters to their loved ones. Given that we now get many thousands more people regularly shopping in West Bromwich, it seemed silly not to allow people to post the cards and letters in a convenient place.”
He added: "After maintaining pressure on the company, I'm pleased to say they have listened to the views of local people. A new post box will now be installed, which I know will be welcomed by many shoppers."
In a letter to Mr Watson, Royal Mail said they would install the post box as quickly as possible.
Steve Burr, centre manager for New Square, said: "We look forward to having the new post box on our site to support the Post Office, New Square and our customers."