Royal Mail delivered an above-average performance in the HX postcode area between April and June 2012.
Figures showed 95.2 per cent of First Class mail was delivered on time - the next day after posting - the national target is 93 per cent.
Royal Mail also exceeded its national Second Class mail and Standard Retail Parcels quality targets.
In the April to June period the overwhelming majority of all mail was delivered on or ahead of target.
The company delivered 98.6 per cent of Second Class mail three working days after posting, beating the 98.5 per cent target, according to independent research.
Standard Retail Parcels beat its 90.0 per cent target of delivery within three working days with a 97.1 per cent performance.
The figures were achieved amid a huge modernisation programme involving new technology and changes to working practices for postmen and women.