Unexpected 552

[#1]

I've been informed that an incoming mail message was 552'd. The message seems innocuous enough, its from a public body using Office 365 etc with a pdf attachment. I don't think there are any URLs in the message at all. What can I do. I've turned off the obvious spam filter, but don't want that off for long. 

Jim C

[#2]

Are you using Plusnet email? or another ISP Email?

Most likely cause is that it has one or more attachments which are too large. Typically 20 - 25Mb is the limit, not sure with Plusnet but I seem to recall it's quite low, less than 10 ?

If it's from a public body it may well have reams of regulations, terms, warnings etc which you'll probably not read anyway.

I was told (advised) a long time ago to stay away from ISP email services as they tend to be an after thought and often a bit quirky! Plus if you change ISP you'll most likely loose access to it anyway. Plusnet seem to be in the process of scrapping theirs.

Much better to use a web based one like gmail, gmx, proton etc

[#3]

The attachment is 1.6MB, and when I forwarded a copy from gmail it went through fine. 

[#4]

Forwarded from Gmail is not the same as being sent DIRECT to the Plusnet address by the sender.

What is the precise delivery process here?

Elsewhere I’m aware of anecdotal evidence of emails with attachments which pass through a forwarding service being rejected because the attachment headers become corrupted by the forwarding (SRS) service. Yes it is technically complex thus precise details are essential to understand your experience.

[#5]

The message was originally sent directly to Plusnet and bounced with the 552. I had the sender resend the message to my Gmail account, and from there I forwarded it to the Plusnet hosted mail address. It got to me that time. That suggests that neither the attachment nor the message body were the primary cause. Normally the first guess would be that the sending host was on a block list, but because the sending host was a Ms Office365 facility it seems less likely. Of course the 552 doesnt give any clues as to why it was blocked, which is sensible and correct, but irritating. Nor do I seem to have any access to logs for blocked messages, which is harder to justify but I suppose precious few would understand them.

JimC

[#6]

Thank you, that’s really helpful. It suggests that the issue might not be the content nor the attachment but some characteristic of the sender.

Elsewhere (CAMRA) I’ve encountered issues with mail sent from Office 365 being blocked after Spamcop blocked a ranger of Office 365 IP addresses. I do not know if that got fixed by Spamcop ~ CAMRA somply whitelisted the IP addresses.

In yet another environment our AWS hosted email service cannot send to @outlook, @live, @hotmail … or indeed to Plusnet hosted email addresses. Outlook.com advises that the AWS platform has a very poor reputation and thus has no intention of lifting the black listing.

I’m seeking deeper engagement with Plusnet on addressing false - positive SPAM assessments. I’ll add this one to the list.