Sophos XG Email MTA mode for inbound only

Good day. I'd like to setup my Sophos XG 17 with MTA mail protection, but I have problems with outbound email.

To simplify, I need to bypass sophos MTA engine for outbound emails, because my internal SMTP (exchange) should delivery using particular Sender Based Routing Policy, towards different public Smart Host (different public smtp, i.e. Google, Microsoft, and so on, based on public email account).

When using MTA mode, actually the firewall acts as SMTP server, and intercept LAN all traffic towards public smtp, and the tries to relay.

In Sophos I see I can use only 1 smart host with MTA mode, and if I don't use the smart host option, the firewall tries to delivery directly to destination smtp, by querying public mx records (I suppose).

I can bypass the problem using Sophos in legagy mode, to let internal SMTP talking directly with public SMTPs, but spam/malware filtering for inbound is not working properly, and I can't see email logs in dashboard, that's why I'd like to stay on MTA mode.

Any suggestions?

Thanks

Andrea