Another mail problem

[#1]

I'm still new here, so probably reposting something that is well known, but...

My email has been swung on my domain from Demon to Plusnet. I use ebay a bit and have been seeing that I get bounce messages for some of the ebay emails rather than the actual email. About 1 in 10 seems to be bounced and identified as spam. The message is as follows

SMTP error from remote server for TEXT command, host: mx.avasin.plus.net
(212.159.8.200) reason: 552 Spam Message Rejected

That message related ot one from ebay that was to inform me that a bid had been successful, so was definitely not spam, although most of the rejected messages are genuine ebay junkmail.

Now today I have had a torrid time on the phone to ebay support, because my ebay screen suddenly disappeared behind a box saying that my main email address was not valid. This is the address that they have for messages and confirmation of account details etc. Their system insists that this email is not valid, so I seem to have to provide a new email address for them.

Any comments?

[#2]

Hmmm, no replies, so perhaps I'm the only one that has had this? I posted before in a bit of a rush, so here goes with the problem:

Plusnet seemed to be bouncing a few emails to me from ebay and saying they are spam. Some are, at least one is obviously not spam.

ebay seems to have seen the bounces and  invoked a pop-up saying that my email address is invalid. This affects some of my administration with ebay, although it appears that I am still logged in on a second machine and still receiving emails from them.

ebay support seemed not to understand what I was talking about, but said about 3 times "Try it now" and suddenly I was able to log in again.

I have now disabled PN spam filtering, and all seems to be OK.

Sometimes I see bounces (not sure that I want spam to be bounced rather than just labelled), and I've also seen a message marked [-spam-]. Is this latter message being filtered somewhere else (my 1 & 1 redirect perhaps?) or is it a different PN filter?