NAT for both port 443 and 80
On NAT rule for NATting incoming connection on WAN - port 80 (VLAN, whatever - at this point VLAN is just a LAN) device - web server.
And another NAT rule for port 443
Both TCP-only, probably.
if I need to make use of 443 to the (for instance) mail host and 443 for my web server which is another host?
Ah, welcome the the club !
A NAT rule includes a port - and taht port will get Network Address translated to another device, some where on LAN.
But, guess what, NAT is PAT most of the time, so, PAT port 444 on WAN to port 443 on LAN (your web mail server).
Inform users that they should use http://your-dyndns.tld:444 and they see the login screen of the web mail web server.