Alan Fryer says he was frantically trying to check his messages Thursday afternoon when the outage occurred, affecting about 70 per cent of Shaw's customers.
"I was in a meeting and I kept checking my iPhone expecting emails, at 3, 4, 5, no email," said Fryer, who is a Shaw customer.
Shaw didn't send out an email to its customers until Saturday.
The letter started with an apology and then told customers that while technicians wouldn't be able to retrieve content of the lost messages, they would be able to recover the name of the sender and the subject of the email.
Fryer said he went to the Shaw web page late last week to find out what was going on, but found nothing. He also tried calling the company, but was put on hold.
"It should not be up to us as customers to pursue a company to find out what's going on," Fryer told CBC News.
"Things go wrong, we understand that, but from my point of view, they weren't proactive. People should email Shaw and say I'm not happy and would like you to be more forthcoming."
Shaw has almost two million internet customers, most of them are in Western Canada.
Last July, an electrical explosion and fire at Shaw's downtown Calgary headquarters caused an Alberta-wide system outage, disabling a number of computer networks, including key municipal and provincial services.
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