The Canadian Union of Postal Workers (CUPW) has begun striking in select cities as of 12:01 am local time.  Here's the official alert from Canada Post:

The Canadian Union of Postal Workers (CUPW) started rotating strikes after 12:01 am (local time) in and around Victoria, Edmonton, Windsor and Halifax. The rotating strikes are expected to last 24 hours. In those areas, mail and parcels will not be delivered or picked up today.
 
Canada Post continues to operate across Canada. We are accepting and delivering mail and parcels in all other locations.
 
We remain committed to arriving at a negotiated settlement with CUPW, while making every effort to minimize the impact of any disruption on the customers we serve.


IMS and Canada Post will continue to collect, process, and deliver your mail and parcels.  We've been through this before and have seen very minimal to no disruptions.  We'll continue to monitor and update the situation as needed. 

The link to updates from Canada Post can be found  here.