Royal Mail has started moving “limited volumes” of export parcels following the recent cyber incident.
The company said it was trialling “operational workarounds” but continued to ask customers not to submit any new export parcels into the network.
A statement said: “Our initial focus will be to clear mail that has already been processed and is waiting to be despatched.
“We are pleased to announce that we have resumed the export of letters which do not require a customs declaration to all international destinations.
“From 1900 this evening, customers will be able to start submitting international export letters which do not require a customs declaration into the Royal Mail network again through all channels including Royal Mail post boxes and Post Office branches.
“Royal Mail continues to work with external experts, the security authorities and regulators to mitigate the impact of this cyber incident, with a focus on restoring all services for export letters and parcels. Our import operations continue to perform a full service with some minor delays. Domestic services remain unaffected.
“We would like to sincerely apologise to impacted customers for any disruption this incident may be causing.”
Royal Mail added it was “working around the clock” to fully resolve the situation.