We are running into an issue with the Message ID header being set incorrectly in version 18.6 and so are looking to upgrade to the latest Aspose.Email library, which appears to be 21.5. It appears, however, that APIs have changed and we are not seeing clear documentation about how the new API structure is supposed to be used. Specifically, BeginSend/EndSend no longer exist in 21.5. There is a SendAsync, but there isn’t a clear way to use a CancellationToken with this method. The ConnectionTimeout property also no longer appears to be available and it isn’t clear what the appropriate substitute is supposed to be.
Note that the API documentation on the Web site (https://reference.aspose.com/email/net/aspose.email.clients.smtp/smtpclient) still references version 21.3 and talks about BeginSend/EndSend, but those methods don’t appear to exist in 21.5. Similarly, I found a .chm file in the Help subdirectory of my NuGet package install that seems to reference version 21.1. I also looked in the release notes and can’t find any indication of such breaking changes to the API. Where should we expect to find documentation of breaking changes of this kind?