This has got nothing to do with hosting your own equipment like routers (with recent regulatory changes, all ISPs in the US are now required to allow this - i.e. be able to run your own equipment without paying a monthly fee to the ISP).
But this is more about ISPs blocking sending on specific ports like port 25 for SMTP. Instead you need to use some mail relay to send your email, who in turn will send the mail over SMTP on port 25.
Some ISPs in the US do allow port 25 SMTP, but very few and none of the large ones like Comcast, AT&T, Verizon.
This has got nothing to do with hosting your own equipment like routers (with recent regulatory changes, all ISPs in the US are now required to allow this - i.e. be able to run your own equipment without paying a monthly fee to the ISP).
But this is more about ISPs blocking sending on specific ports like port 25 for SMTP. Instead you need to use some mail relay to send your email, who in turn will send the mail over SMTP on port 25.
Some ISPs in the US do allow port 25 SMTP, but very few and none of the large ones like Comcast, AT&T, Verizon.