Some of the mail - including a Hello Kitty doll that Irene Cook bought for her granddaughter - that was found dumped on Auckland's North Shore.

Mailed gifts and cash have been stolen from Aucklanders' letterboxes just days out from Christmas.

​Police began investigating after a significant amount of mail was found dumped in Auckland.

The Hauraki, Belmont and Bayswater areas of the North Shore were all hit by the thieves, who were believed to be targeting gifts and money sent in the mail, a police spokesman said.

Irene Cook's Christmas present for her granddaughter was among the gifts that were swiped.

"My granddaughter told her dad, my son, she really wanted a Hello Kitty doll for Christmas, and it was an absolute mission to find one," she said.

"I ended up getting in contact with a lady in Glenfield, who kindly wrapped it for me and even included a necklace and bracelet with it."

A few days after the woman had posted the gift, it had still not arrived, Cook said.

She had begun to lose hope it ever would until she saw a North Shore Police Facebook post about the stolen mail.

"You could see the Hello Kitty doll right there in the photo!" Cook said.

"I contacted the Takapuna Police and thankfully my daughter-in-law gets to pick up the gift tomorrow.

"It's sad that my granddaughter nearly had to miss out on her Christmas present, especially when she was counting on me to come through."

Cook felt very relieved the doll had been found but said sadly, the necklace and bracelet had not been located.

The stolen mail had been sent away to be forensically tested and would be picked up by NZ Post on Friday to be delivered to the correct recipients in the next couple of days, a police spokesman said.

Police encouraged residents to clear their mailboxes daily, get parcels delivered by registered post, ask a neighbour to clear the mail while they were away, and install a lock on the mailbox.

Anyone with information in relation to the thefts was asked to contact North Shore Police constable Jasmine Bundle on 09 477 5000.

A NZ Post spokeswoman said the company was concerned to hear of the thefts and was working with police after the delivered mail was dumped.

"We also do encourage customers to contact us via our website as soon as possible if they do not receive a parcel they are expecting," she said.

"For security and convenience, we have a range of delivery options available for our customers, including the ability to have parcels directed to a one of our 180 parcel collect locations nationwide, or you can also give us the authority to leave your parcel somewhere safe every time we deliver something and you're not home."

The spokeswoman said if anyone found mail or believed their mail was missing they should call 0800 501 501.