Port 25 is the relay port.
Port 587 is the submission port.
They are NOT interchangeable.
Port 465 is deprecated and should not be used in any case.
If you want to send mail and your host blocks port 25, you have two options:
- Use a relay service as @calport advised.
- Change your provider.
No, it’s not. Web hosts are businesses selling to other businesses. Blocking a port needed for communication would be like the telephone company telling you that you can have a handset, but no line; or the electric company telling you that you can have a light bulb, but no socket for it.
My answer to your problem would be to find a better host.
Part of the problem is that many hosting companies want to automate everything, so literally anyone can open an account with no human intervention. The host I use doesn’t. They manually verify a new client’s identity, address, and business license, and require a business credit card, before activating the client’s first server. But they don’t block any ports.
They made an exception in my case because they were aware of the meltdown that was going on at HFW: but only after a senior support tech interviewed me over the phone, decided I sounded legit, and checked the reputation of the IP on the server I was leaving. They let me migrate overnight (on Christmas Eve!), and do the paperwork the next business day.
I would run – not walk – away from any hosting company that blocked any service port. But I guess that’s just me, because there are many companies that do.