Seven postal runs in Newcastle and Lake Macquarie were missed on Monday, leaving thousands of premises without a mail delivery.
Australia Post says the shortfall was due to a “higher than normal” number of staff on sick leave.
But an employee of more than a decade, who spoke on the condition of anonymity, blamed short-staffing.
He said four relief staff had been enlisted from Sydney to work in the Hunter since Christmas, but they were returning home at the end of this week.
The employee also said the introduction of electric buggies had made mail rounds much slower than traditional postie bikes, but Australia Post would not comment on this.
The Newcastle Herald understands premises in Mayfield, Hamilton, Islington, Merewether Heights, Wallsend, Lambton and Fletcher were among those that missed out on Monday’s deliveries.
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An Australia Post spokesperson said all express, registered and priority mail reached its destination on Monday and undelivered mail was dropped off on Tuesday.
The latest hiccough came after two mail rounds were affected on different days last week, which Australia Post also attributed to absent staff.