It’s available in theory but disabled for tenants “who don’t use it” which in practice means an IT department needs to manually specify a new policy to allow it. I think that’s likely to be a non-starter for us, but will make some requests. For info, this is the default response from smtp server now:
EHLO
250-XXX.outlook.office365.com Hello [178.XXX.XXX.XXX]
250-SIZE 157286400
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250 SMTPUTF8