Like I said not going to hurt anything... But amount of places that actually have those ports open at the isp level is not very much.. More an exercise in how to do it more than actual security..
Here is from one of my vps box out of the net
Starting Nmap 7.01 ( https://nmap.org ) at 2019-06-02 09:54 CDT
Nmap scan report for scanme.nmap.org (45.33.32.156)
Host is up (0.015s latency).
Other addresses for scanme.nmap.org (not scanned): 2600:3c01::f03c:91ff:fe18:bb2f
Not shown: 1022 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
Nmap done: 1 IP address (1 host up) scanned in 1.96 seconds
Here is from my home connection
Starting Nmap 7.01 ( https://nmap.org ) at 2019-06-02 09:48 CDT
Nmap scan report for scanme.nmap.org (45.33.32.156)
Host is up (0.062s latency).
Other addresses for scanme.nmap.org (not scanned): 2600:3c01::f03c:91ff:fe18:bb2f
Not shown: 1012 closed ports
PORT STATE SERVICE
22/tcp open ssh
25/tcp filtered smtp
55/tcp filtered isi-gl
67/tcp filtered dhcps
77/tcp filtered priv-rje
80/tcp open http
135/tcp filtered msrpc
137/tcp filtered netbios-ns
138/tcp filtered netbios-dgm
139/tcp filtered netbios-ssn
445/tcp filtered microsoft-ds
496/tcp filtered pim-rp-disc
Nmap done: 1 IP address (1 host up) scanned in 322.31 seconds
As you see 25 blocked by isp as well.. Home connections that is almost always blocked as well.. But if your on some sort of fiber...
