DNS Setup when Hosting Email at Home

[#1]

Hi,
I need to test an Email setup on my broadband connection, this is for a charity where I help support IT.
The requirement is for Email that is not encrypted so that faults on the network can be sent outward.
There is no need for inward Email to reach the mail server.
The Email prog that fits the bill is hMailServer
Testing is easier at home and once working I can change the charity setup to suit.
Apparently I need to setup a domain to perform the Email test and then make a DNS  MX record pointing to the IP address of the mail server (or the external address of internet router)  This seems easier to setup pointing to my external IP address as the PC with hMailserver will be behind my Internet router.
As I don't have a domain as such with Plusnet, or I assume not,  just my email address then I'm wondering if I can use a domain name I already own.  With the domain name I own is an Email account too which I use via a web interface  i.e. I don't use Outlook or Thunderbird etc.    I can see on this companies site the ability to change my domain MX record from them, to anything else I want, but what I'm afraid of is messing  up my Email with them if I change this record.
So is there a way to setup my own Email server using my existing domain name without messing up my existing Email.

[#2]

Hi and welcome to the PN forum!
MX records are only required if your email server is receiving inbound email.  Outbound email shouldn't require any special configuration though you need to be aware that many email servers will reject email that seems to be coming from a domestic ISP connection.
Is there a reason for not sending through the Plusnet outgoing server rather than through your own server?

[#3]

Hi,
Thanks for the info.
I am not new to IT support but quite new to Email and DNS.
I thought that to forward mail via my ISP the mail server had to do something like SMTP forwarding?  Which I think is turned off on most ISPs mail servers.
Would forwarding work coming from ANY  Internet connection,  i.e. when finally implemented mail has to emerge from the charities Internet connection.

[#4]

To add to that..
It would be useful just for the test to receive incoming Email just to see that working, but to prevent SPAM incoming would be off

[#5]

I've been there and done all of this.
I created an MTA on a linux server at home. I used sendmail as it is used extensively in the real world.
Firstly you will need to create MX records to point to your server. This is the public address side of your gateway. If you are using NAT then you will  have to translate and forward to the IP address of your MTA.
Now that is the easy bit!
I found within hours I was receiving no end of spam so I implemented reverse DNS verification and Black listing via Spamhaus. This certainly helped but the change brought to my attentions I did not have a reverse DNS record myself so a lot of my outgoing mail was be rejected at the next MTA in the chain. All I will say is best of luck with Plusnet!
I succeeded as I was not with Plusnet then but a choir it certainly was.
All worked fine and would probably still be working today. However along comes new protocols called SPF and DKIM (well not new but then there was little uptake). Most of the big boys now need these to verify you so you would have to create them. Not difficult but a pain in the bottom.
Could I stop the spam - no! so I looked for another solution. Google apps just fitted the bill and that is where I went with all the charity work. I was fortunate because setting up was free with unlimited resource however that was subsequently reduced and finally stopped altogether. Charities and School related services still  had free access but the US would NOT recognize anyone outside the USA. I begged and pleaded to no avail.  However, I can now report this has changed and provided your charity is registered with the UK charities commission you should get the service for free.
The advantages are enormous - 7+GB mail storage per email address!!!!!!
Local cloud storage etc.
The interface is still very quirky and changes frequently but you don't have to manage and your getting the reliability of one of the biggest email providers
So to sum up - don't bother its too much like hard work but If your up for a big challenge or some self learning it is feasible.