Royal Mail is the company that delivers parcels and letters – the provider of the universal postal service.

Households across the UK can expect mail to be delivered six days a week, Monday to Saturday. However, this isn't always possible for several reasons.

Royal Mail may be unable to deliver mail in some situations, such as when the address is unsafe or inaccessible, the postman can't gain entry to the address, or the letter or package isn't properly packaged.

Sometimes, issues with the movement of mail through Royal Mail networks may cause disruption, but the postal service reported that everything "operated to schedule" over the weekend.

While its air, rail, road and mail centre networks are free of disruption today, Monday, January 13, Royal Mail has warned of delivery delays across the country.

The postal service said that timely deliveries, six days a week, may temporarily not be possible in several local offices due to local issues.

Royal Mail said that high levels of sick absence, resourcing, or other local factors may influence operations in delivery offices. Customers have been reassured: "In those cases, we [Royal Mail] will rotate deliveries to minimise the delay to individual customers."

According to the postal service, 33 postcodes are "most impacted" by delays today, including three that the Boston Delivery Office in Lancashire services. Four Oxford East postcodes and three in Manchester South East are listed today.

Express.co.uk has rounded up the full list - is your postcode area affected?