Mail posted from Bendigo will now take two days to reach someone in Melbourne, with non-local mail sorted in Dandenong as of Monday. 

However local delivery within postcodes 3550 to 3556 will be sorted in Bendigo and remain next-day delivery.

Australia Post spokeswoman Michelle Skehan said the changes had been made to adapt to rapidly declining mail volumes.

She said the arrangement would help meet community service obligations and the requirement of 94 per cent of letters delivered on-time or early.

"We appreciate the impact this may have on some residents in these areas," Ms Skehan said. 

"However, losses in our domestic mail business have grown by almost 60 per cent to $218.4 million last financial year and, if unchecked, would significantly impact our ability to continue to deliver an efficient and cost-effective national mail service for Australian consumers and businesses."

Member for Bendigo Lisa Chesters said the changes would see a "second-rate service" rolled out across country Victoria. 

"Australia Post made some concessions when it comes to mail in the postcodes of 3550-3556, and mail will still be sorted in Bendigo," she said. 

"However, it's still not good enough. The changes will effect central Victorian towns such as Raywood, Castlemaine and Heathcote, who will still wait twice as long to receive their mail as their mail will go via Dandenong."

She said maintaining a reliable postal service was a vital part of Bendigo’s infrastructure.

"Right now, Bendigo is booming. We have economic growth. It is a vibrant region with a proud history and an exciting future," she said. 

"However, this growth will be under threat if we continue to lose core services like Australia Post."