Mail server

[#1]

My mail setup has always been to have my client machines pointing at my own mail server, which simply acts as a central mailbox, fetching mail from my PlusNet mailboxes. I'm fairly sure that I used to have my mail clients pointing at my mail server for sending too, with it just relaying to the PlusNet SMTP server, but I switched clients a while ago and couldn't get it to work unless I set it to point directly at relay.plus.net.
No big deal really, but I'd quite like to be able to go via my own server again (just gives a single point to update if necessary) and I'm a bit puzzled about why it no longer seems to be working. It seems unlikely that something changed at PlusNet just at the time as I changed my mail client software, so I'm assuming I've just done something stupid or forgotten a necessary step.
Any ideas?

[#2]

First off, what errors are your clients getting when sending?
Nothing has changed recently that would prohibit the process you have described. Though there are potential account related settings that could prohibit it, which will have not changed unless you have done so via the portal, or in some cases account changes.

[#3]

It was some months ago that I encountered the problem and I didn't have the time to investigate it at the time - it only came to mind again today when I was setting up a mobile device and remembered that I no longer seem to be able just to point at my own server. I thought I'd just check first off whether there was a known change or if I had remembered incorrectly and that it never worked that way. Evidently not.
I'll try some poking around on my laptop and see if I can get some more useful information to report.
Thanks for the reply.
[Edit] Working fine now, so I can only assume that I did something wrong in the earlier rush to get things working. Apologies for the false call.