Unfortunately, many VPS vendors block port 25 (which is for SMTP) these days, especially in low-cost plans. Let’s assume one cannot change that.
This thread discusses the options to mitigate port 25 blockage.
So, in MiaB you run into this message:
> Outbound mail (SMTP port 25) seems to be blocked by your network. > You will not be able to send any mail. > Many residential networks block port 25 to prevent hijacked machines > from being able to send spam. > A quick connection test to Google’s mail server on port 25 failed.
Well, you probably knew this ahead of time. What you didn’t know is that there is a wholesale industry conspiracy around port 25 blockage to rip off their “valued customers” or however they put it these days.
Now what are the options?
obviously, they ought to be free of charge i.e. 0 € or $ like netcat or socat
No, this thread is. You are looking for solutions for problems that do not exist. If one provider does not want a mail server to be run on their network, you move on to a provider who allows such.
MOST people who are interested in this project are going to be willing to put out the few dollars/euro that is required to rent a VPS service from a provider rather than wanting to deal with jumping through hoops to get something for nothing.
You said it yourself …
so they are out there … as a matter of fact, I have yet to run into a vendor who would not allow mail other than one of the following - Microsoft, Google, Amazon. I do not remember which of those 3 do not allow mail other than Amazon … maybe it is all of them? I do not know nor do I care as all 3 are antathema to this project.
When we call software “free,” we mean that it respects the users’ essential freedoms: the freedom to run it, to study and change it, and to redistribute copies with or without changes. This is a matter of freedom, not price, so think of “free speech,” not “free beer.”
Actually, Amazon has no issues with running mail servers on their platform, so long as you’re using it for legitimate purposes. If you want to be as cheap as possible, you can even run it on a $3 per month EC2 instance.