Royal Mail customers have been left unable to track letters and parcels, with the service experiencing technical issues online.
Website Downdetector said it's seen a 94% spike in reported issues over the past hour - with tracking the primary concern.
"@RoyalMail having a problem generating an RMA, the form on the website returns a non-valid email address error when I give my (valid) gmail address. If it is intended to not accept gmail addresses, then the error should be more specific- otherwise, can you fix the bug," one user wrote on twitter.
Another said: "@RoyalMail’s tracking gone down for anyone else? Can’t seem to trace any of my parcels".
Mirror Money has contacted Royal Mail for a status update, which appears to be affecting online tracking numbers.
The issue comes just a week after the service made the decision to axe Saturday letter deliveries due to staff shortages during the coronavirus pandemic.
The firm said it has 'temporarily' cut back its services, with Saturday first and second class letter deliveries to be paused until further notice.
But most parcels - including Tracked, Special Delivery and non-account services - will not be impacted and posties will continue to pick up from branches and boxes as normal.
It comes as union leaders are encouraging postmen to call in sick rather than risk catching coronavirus during their daily rounds.
Last month the Communication Workers' Union, which represents postal workers, tried to lobby for home deliveries to be reduced to three days a week, with postmen dropping off items on alternate days, but this was shelved.
Royal Mail's chief customer officer Nick Landon said postmen have faced 'incredible pressure' and 'need some relief' in a video shared with workers.
In a statement, Royal Mail said: "Our postmen and postwomen are working very hard across the UK in challenging conditions," the organisation explained.
"As we said at the start of the coronavirus crisis, there will be some disruption to services.
"Relevant factors include high levels of coronavirus-related absences and necessary social distancing measures.
"We understand the importance of the postal service in keeping the UK connected at this time. We have also listened to our hard-working colleagues who have asked us to ease the additional burden on them if possible.
"As a result, we are making some temporary changes to postal services.Q
"Customers should continue to post both letters and parcels as usual on Saturday. We will continue our Saturday collections from businesses, post offices and post boxes as normal.
"From 2 May we will temporarily no longer deliver letters on a Saturday. We will continue to provide a letter delivery service from Monday to Friday as normal.
"We will continue to deliver Special Delivery, Tracked, all non-account services and most other parcels from Monday to Saturday across the country."
Other third party delivery firms such as Parcel Force and UPS will be unaffected by the announcement.
