Lost connection with {hostname[ip]} wile receiving the initial server greeting

Hi Guys
I am wondering if someone can point me in the right direction.
I have noticed a few domains pop up in my mail queue.
They are all trying to connect to mx0.123-reg.co.uk (94.136.40.61)(94.136.40.152)(94.136.40.150)
https://i.imgur.com/gQFaPUg.png
Is there anything I can check my end before I start talking with 123-reg.co.uk
KRs
Dex

 

Yes I have and I am not on any lists. 123-reg even checked to see if I was listed on anything.

I have spoken with their dedicated support team, and they have said that there does not appear to be a problem with my IP address their end and basically wouldn't talk to me because I was not a customer. That doesn't help me my end though, as I have clients who are getting frustrated as they are Solicitors, and it slows down progress

Is there anything I can check, to see why they are not letting me in? I have been reading about bypassing postfix and using telnet to test, but i have never done this. Any suggestions?

Thanks again!