Up to 1,000 postal workers on Merseyside are attending a meeting after three days of unofficial strikes.
Workers said they got to work and were told they had to start later
Union leaders are reporting back to members after talks with Royal Mail aimed at finding a solution to the dispute which has disrupted services.
The walkout, prompted by a row over shift patterns, began on Wednesday after staff turned up for work.
Royal Mail has condemned the illegal action in Liverpool and called the stoppage "wholly unacceptable".
Managers said they are doing everything they can to maintain some services such as special delivery and mail collections.
There had been talks with local union representatives on Thursday about altering some of the current shift patterns.
Workers outside Liverpool's Copperas Hill delivery office said they were protesting after being greeted with the changes made by executives.
Deliveries to Liverpool, Wirral and west Lancashire are all affected.
The Communications Workers Union (CWU) has claimed Royal Mail in Liverpool has refused to renegotiate on shift times.
Mike Yarwood, area delivery representative for the CWU, said: "The area general manager for the Royal Mail is not prepared to renegotiate on what he has already proposed to us.
"We are collating information and will put it to our members later.
"The negotiations are about the different shift times. We have to make sure that it is right for our people."
The meeting is being held at Aintree racecourse.