FYI, this is what the email said
Dear Applicant,
Please confirm your valid mailing address with us. Please note that if you are currently living abroad your documentation will be sent via regular mail, which does not allow for tracking. However, if you reside in Canada, please provide us with a shipping label to safely return your documentation.
Please reply to this email as soon as possible.
Regards,
Xxx
Immigration, Refugees and Citizenship Canada | Immigration, Réfugiés et Citoyenneté Canada
Government of Canada | Gouvernement du Canada
www.cic.gc.ca
INSTRUCTIONS FOR A XPRESSPOST LAB
For secure delivery to Canada and the USA, we strongly suggest that you purchase a Canada Post Xpresspost label. Please see the instructions and the link below:
http://www.canadapost.ca/personal/tools/cst/intro-e.asp
Please follow these instructions carefully:
1) Click on the link above
2) Select the shipping destination
3) Enter the CPC-Ottawa mailing address in the Ship From Address section.
First Name: CPC
Last Name: Ottawa
Email: (Your email address)
Street Number: 365
Street Name: Laurier Ave
Direction: West
City: Ottawa
Province: Ontario
Postal Code: K1A 1L1
4) Fill in the Ship To Address section with your mailing details
5) Describe Item: Weight (kg): 0.200g, Length (cm): 24 Width: 16 Height: 1
6) Select your service (Priority, Xpresspost etc).
7) Review all mailing details and pay online.
8) Email yourself and save your Xpresspost label as an electronic version (PDF file) on your computer or smart phone.
9) Email the label as an attachment to CPC-CTD-Ottawa@cic.gc.ca
Once our office receives your Xpresspost slip attachment, we will print and affix the label to an envelope and mail out your documents.