One of the biggest trade unions will today decide who to support in the Labour leadership contest.
The Communication Workers Union is expected to back Jeremy Corbyn, having supported him in last year's election.
Union activists will meet in London to make the decision.
The CWU has around 200,000 members in the Royal Mail, Post Office, BT and other firms.
Mr Corbyn has already received the support of unions including the train drivers' Aslef and construction workers' Ucatt.