Since SNOV.IO is a third party service, sorry I am not quite familiar with it.
Snov have said turn on 2FA (which I've done) and then set up an app password (which it doesnt look like I can do).
About how to set up an app password, please follow the suggestions in this link:
How to setup app password in Exchange 365?
If MFA has been enabled for your account, you may see the option to add a App password.
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