The postal service said the older neighbourhoods and smaller lots in urban cores present different challenges for locating community mailboxes than suburban areas.
So, Canada Post says it will leave the majority of those areas until the final stage of its plan to phase out door-to-door mail delivery.
"The postal service will take the necessary time to understand their unique needs and find solutions that work for these neighbourhoods," Canada Post said in a statement.
The postal service also said it was working to address the needs of seniors and disabled Canadians.
"Canada Post is developing alternative approaches for people with significant mobility challenges, who lack viable alternatives and upon whom delivery to a community mailbox would impose an unacceptable hardship," it said.
The post office was widely criticized when it announced its plan to phase out home delivery late last year. Under the plan, mail for those who currently receive door-to-door service will be delivered to communal neighbourhood "superboxes."
About one-third of Canadian households receive their mail at their door. The rest pick up their mail at a central location, like an apartment lobby or community mailbox, or rural mailboxes.
The federal Crown corporation has said it hopes to realize up to $900 million a year under the plan to replace home delivery with community mail boxes and by raising postal rates and cutting thousands of jobs.
The move to community mail boxes is expected to account for $400 million to $500 million in savings once it is fully implemented.
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