email not being received, returned to sender quoting Error 552

[#1]

The anti-spam heuristics we depend on use real time threat reporting. An email considered clean one day may well be considered spam the next. If you message me the address of the sender who's unable to contact you then I'll see if I can fix things for you.

[#2]

Thanks Bob,
It's one of 2 possible address -
1.  xxxxxxxxxxxx@hotmail.com (most likely), or
2. xxxxxxxxxxxx@theambassadors.com
Out of interest - I can't find my spam folder anywhere - where is (in my webmail?)
[Moderator's note by Dick (Strat) Full email addresses edited in a public forum.

[#3]

There's nothing wrong with either of those addresses as far as our spam filters are concerned, so it must be something else within the body of the email, or the sending server itself that's causing the rejection. If you can get the sender to send the email to a non-Plusnet email address you have and provide me with the full headers of the received message, then I should be able to work out what's going on.
BTW, it's ill-advised to post email addresses on a public forum like this. It's likely to result in spambots indexing the address and sending junk to it. I've asked the mods to remove/munge the addresses in your post.
The Spam folder should be visible in Webmail, or be available to subscribe to if you're using IMAP. If you're using POP3 then you won't be able to see it.

[#4]

PM to you also Bob.
Thank you
John

[#5]

Many thanks, Bob, for your Message indicating that my problem has been fixed.  A test message confirms your statement.
I am most grateful for the trouble you have taken on my behalf and, indeed, for your accurate diagnosis in the first place.
Most professional.
Regards.....Noel

[#6]

No worries Noel, glad to hear it's sorted