SFOS 19.0 MR1 new email option

No, that is not possible. This option is is more likely something to report back to SophosLabs. 

You could check Central Email instead. Waiting on a firmware update on a security product is not a wise move. 

"Waiting on a firmware update on a security product is not a wise move" - I understand your argument and share it too.
If I would update to the newest firmware now, the possibilty for phising/malware will increase (with the bug at the moment) and therefore your argument will bring me in much more troubles. I'am the first who update the systems to the last.
But on the other hand there is a problem (which popped up with an update) with the product we bought and now we should switch to another mail protection product (and pay additionally to the existing one) from Sophos because there is serveral months no fix for the poor spam regonization with SASI on XG(S) firewalls?

Nevertheless my question is answered, thanks Lucar!

"Waiting on a firmware update on a security product is not a wise move" - I understand your argument and share it too.
If I would update to the newest firmware now, the possibilty for phising/malware will increase (with the bug at the moment) and therefore your argument will bring me in much more troubles. I'am the first who update the systems to the last.
But on the other hand there is a problem (which popped up with an update) with the product we bought and now we should switch to another mail protection product (and pay additionally to the existing one) from Sophos because there is serveral months no fix for the poor spam regonization with SASI on XG(S) firewalls?

Nevertheless my question is answered, thanks Lucar!

If I would update to the newest firmware now, the possibilty for phising/malware will increase (with the bug at the moment) and therefore your argument will bring me in much more troubles. I'am the first who update the systems to the last.

That is actually not correct.

Spam =!= Malware. Spam is likely just unwanted Emails. See definition of Spam. So phising/malware is a different concern. If you find a valid malware or phising Email coming through, the question is, which module should fetch this attack. SFOS/UTM does not have good modules to detect phising in the first place (never had). Malware is something, which we can fetch with Intelix/Zero Day. 

If an advertising Email gets through, which could be considered as Spamming (bulk), this is a security concern per se - Only annoying for the end user. 

So if your concerns are security related, the only move would be to check the solutions for valid BEC and modern technologies. 

We use the Xstream Protection bundle with Email Protection and zero-day protection activated in MTA. Will those mails be checked for beeing spam with zero-day protection too or only on the XG itself?

Zero Day Protection is a malware battle technique. Intelix is being used in SFOS to detect attacks, not Spam.