Australia Post has been told to make it easier for customers to lodge complaints online after the Commonwealth Ombudsman identified persistent delivery issues.

The ombudsman has made six recommendations aimed at reducing the number of complaints over the notification of failed delivery cards, the Safe Drop program and compensation for lost items.

Commonwealth Ombudsman Michael Manthorpe said complaints to his office fell 30 per cent over the past two years but the company itself received 1.1 million complaints in 2016/17.

That was despite three earlier reports into the same delivery issues.

"While the scale of Australia Post's operations need to be borne in mind to put complaint numbers in perspective, the fact that more than one million people have complained to it is cause for concern," he said in his report released on Tuesday.

There is also evidence from people in contact with his office that some cases which should be classified as complaints are not being counted as such by the company.

"Numerous complainants to our office report that Australia Post was defensive in its dealings with them, or that Australia Post was reluctant to adequately deal with their complaints, including through the provision of compensation," Mr Manthorpe said.

The ombudsman recommended Australia Post make it simpler for customers to lodge an online complaint without the need to create an account.

It also recommended:

* The company review the classification method for recording complaints to ensure they are recorded as such rather than investigations or feedback.

* Australia Post conduct its own review into why people felt the need to take their cases to the ombudsman and why its processes were unable to resolve the matter.

* The company publish clear advice on which addresses which may not be suitable for parcel delivery.

* The quality and consistency of advice provided to customers on compensation is improved.

In a letter to the ombudsman, Australia Post CEO Christine Holgate said she recognised and acknowledged the common themes in the report warrant reflection.

"I want to make it as easy as possible for customers to engage with Australia Post, and to encourage transparency," she said.

The company has accepted five of the six recommendations and has partially accepted the other.

It says changes to its website will mean people can make a complaint without an account.

By the end of June it will also publish information about the types of households and premises which aren't suitable for parcel delivery.