Spam Filter now rejecting perfectly valid emails for no reason?

[#1]

I only have the spam filter on the least aggressive setting but this week I'm getting people telling me you are now all of a sudden bouncing valid emails?

I've tried configuring the whitelist but that's not worked. Quite amazingly the help apparently says that if you have catch all emails on (which I do and is the default) then whitelists don't work which seems pretty mad. WHY! If I say something is in the whitelist then I want it in the whitelist, I don't want you second guessing if that's a good thing or not depending on the other settings? That just seems ridiculous. I trust these email addresses but you won't allow them through, it makes no sense.

I need catch all emails, your spam filter isn't now working properly, and I can't whitelist the people I know I trust? But that would be a sticking plaster anyway, it seems you've done something to break your spam filter., even if I whitelist these email addresses you may be bouncing others I don't know about

PS - you are flat rejecting it, it doesn't get to me marked "Spam", it returns to user with error 552 and I get nothing. These emails have previously worked fine for years.

[#2]

If they've received a 552 error, that means that the email contents or sender are being detected as having a poor reputation, so we block this to ensure our customers don't receive spam. If it's a valid email they can contact us by sending an email to abuse@plus.net with the following detail:

• Subject “Third party email blocked by Plusnet spam filter”
• Clarification that they cannot send email to Plusnet email addresses because the email gets reported as SPAM
• Purpose of the email send and provide a sample of the mail sent.
• Inclusion of errors contained within the NDR (Non Deliverable Report) emails.
• Provide the sender address, subject line, recipient address and date/time in GMT/BST
• Send only one request and set expectations on turnaround

[#3]

I don't want people I deal with to be having to go through all that and wouldn't expect them to, they are people from a large reputable company. I must have exchanged 1000 emails with them over years and this has only just suddenly started happening. Stangely some get through. I'll send something myself to abuse@.

[#4]

Any email MTA even those of "large reputable companies" can fall foul of a virus or trogon infection and start sending spam emails, resulting in their email service acquiring a bad sender's reputation.

Such reputations are not assessed by individual email services such as Plusnet but by email black list monitors. Take a look here - https://mxtoolbox.com/supertoolmobile.aspx - put your sender's domain name in and see what they report.

As for your suggestion that you will put a report into plusnet, you do not have the information required to investigate the matter - that is in the hands of the sender.