Thanks for your answer, but I am still unable to get it working.
When I try to configure Email Settings using the Reporting Services Configuration Manager, it only asks me 2 things: Sender Address and SMTP Server. It never even asks for the password or anything about security. So I have no idea how to specify the authentication type or how to enforce TLS 1.2 or .NET. Here is the section from the rsreportserver.config file about the email settings:
<RSEmailDPConfiguration>
<SMTPServer>smtp.office365.com</SMTPServer>
<SMTPServerPort>
</SMTPServerPort>
<SMTPAccountName>
</SMTPAccountName>
<SMTPConnectionTimeout>
</SMTPConnectionTimeout>
<SMTPServerPickupDirectory>
</SMTPServerPickupDirectory>
<SMTPUseSSL>
</SMTPUseSSL>
<SendUsing>2</SendUsing>
<SMTPAuthenticate>
</SMTPAuthenticate>
<From>******@domainname.com</From>
<EmbeddedRenderFormats>
<RenderingExtension>MHTML</RenderingExtension>
</EmbeddedRenderFormats>
<PrivilegedUserRenderFormats>
</PrivilegedUserRenderFormats>
<ExcludedRenderFormats>
<RenderingExtension>HTMLOWC</RenderingExtension>
<RenderingExtension>NULL</RenderingExtension>
<RenderingExtension>RGDI</RenderingExtension>
</ExcludedRenderFormats>
<SendEmailToUserAlias>True</SendEmailToUserAlias>
<DefaultHostName>
</DefaultHostName>
<PermittedHosts>
</PermittedHosts>
</RSEmailDPConfiguration>
So I'm trying to figure out how I can change this so it will work? It seems like at a minimum I need to store the password somehow, and I might like to specify the port, authentication method, etc as well.