From the WIA, original post here.

Date : 13 / 05 / 2016 
Author : Jim Linton – VK3PC

The Wireless Institute of Australia operates a QSL Bureau system for its members that generally follows the guidelines decided by the International Amateur Radio Union.  Among them are standards for QSL cards.  The IARU has a universal standard for QSL card production to improve the handling of them by volunteers around the world.

The WIA only processes cards that meet the IARU standard.  That is, they should be no larger than 140mm by 90mm, and are at least 0.25mm thick.  Copy paper is not suitable and glossy photographic paper with inkjet printing also causes issues for QSL Bureaux around the world.

All current users and those thinking of having QSL cards printed, need to read to IARU standards and methods used by the WIA including the pre-sorting of cards by those using the outwards bureau.

More information on this WIA membership service is on the WIA website under For Members or via this Link.