The postal regulator is investigating complaints that the final daily collection from some post boxes in England and Wales is now as early as 9am.
The Postcomm inquiry was launched after residents in areas including South Wales, Derbyshire and Ipswich complained that final collections were being made before their post was delivered.
Postcomm has announced a three-month consultation to check details of when post is being collected and delivered before deciding whether to order any changes.
Postcomm Chief Executive Sarah Chambers said 9am seemed ‘very early’ to be collecting post, adding that collection times seemed to be changing ‘gradually’ in some parts of the country.
Ms Chambers added: ‘There may be some parts of the country where post boxes are so remote that the only way Royal Mail can guarantee next-day delivery is to collect post early.
‘People are telling us that in some areas post is being collected as early as 9am, whereas deliveries come later than that. We need to find out what customers really want from their post and then we will decide if anything needs to be done about it.’
A Royal Mail spokesman said: ‘Royal Mail monitors daily the times its drivers make mail collections from post boxes and we are very confident that customers can post their mail knowing that we don’t make the final collection before the last collection time shown on the box.’