According to this page, you have two options:
Using the services of a certified translator who is in good standing with their provincial or territorial organization and certified to translate documents. (Canada)
Using the services of a translator who is accredited (officially recognized or authorized [emphasis mine]) in the country where the translation is being completed. (outside of Canada)
You can start by contacting the CTTIC or OTTIAQ to inquire if there are any certfied translators in Canada. There may also be other provincial orders to contact.
The next step would be to locate any country in the world that officially recognizes Esperanto translators. Logically, if such persons exist, they are likely to be able to translate to English at least.
Note that since the immigration agent has a high degree of discretionary power when evaluating evidence, it may be a good idea to seriously consider whether submitting these messages is 100% necessary in the first place as they might not be receptive to the idea. Less is more when it comes to immigration to Canada: as a rule of thumb, you want to avoid supplying documents that raise additional questions unless you have no other choice.