Titilola Jones, of Southdale Road, North Oxford, discovered about 40 letters, including bank statements, utility bills and junk mail, in a heap in Sunnymead Park on Saturday.
Her two children, Michael, eight, and Temilola, six, helped her scoop up the pile and take it home so that they could alert the police.
Some of the letters had already been opened, including an acceptance letter to a student from a college, water bills and bank statements.
But police and the Royal Mail have said she should wait to hand back the post, despite at least five of the recipients living in her street.
Instead, the pile of letters must be picked up by Royal Mail and sorted again before they can be delivered.
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It is not yet clear whether the mail had been stolen, lost or dumped. Yesterday, the pile of correspondence was still at her home.
Mrs Jones said she reported the discovery to police on Saturday, but they said it was not a criminal matter and gave her a telephone number for the Royal Mail, which was out of date.
She added: "I'm waiting for a cheque myself which has not arrived. When I saw some of the letters open, I got a bit curious. I took them home because I could see some of them belonged to my neighbours.
"The police said they needed to be picked up by the Royal Mail.
"I mentioned I could deliver them because there are five addresses in my street and they said they would rather I didn't.
"I have all this mail and a lot of people are expecting their post.
"If it was me, I would want my mail. I'm tempted to go and deliver them. I don't recognise many names, but some are in my street. If nothing happens, I will deliver them."
The family has been waiting for the Royal Mail to pick them up for the past four days.
Royal Mail spokesman Richard Hall said: "If we are contacted on our customer service line, we will arrange to get the mail picked up and redelivered as quickly as possible.
"She won't get into trouble if she delivers them, but we prefer to deal with it so we can discover what has been recovered. We would prefer to deliver it ourselves so we can put a letter explaining why it has been delivered late or damaged.
"Postal theft is a great inconvenience and concern to our customers and it is something we take seriously."
Police spokesman Toby Shergold said: "It is not necessarily a police matter because the mail could have been lost or dumped.
"We referred the caller to the Royal Mail, but unfortunately they have updated the number.
"We would advise the letters were not delivered but given to the Royal Mail, so they can conduct their own internal inquiry."
Mrs Jones said a group of youths was seen near the bundle of letters in a play area shortly before she found them.
OXFORD SNAIL
Jeeeze can we get any worse
