Some incoming business emails being blocked?

[#1]

We noticed recently that one or two emails sent to either of our .plus.com addresses are being blocked. First it was e-tickets not arriving from a rail company (despite repeated attempts after phoning them), this week a bike centre rang me to say they twice tried to email my address but these were bouncing back with a message that they had been identified as spam. These are not going into our Junk folders, they're not being delivered at all. Is Plusnet mistakenly rejecting business emails as malicious or spam? Is there anything we can do?

[#2]

Please raise a call with the support desk ... and report back here how things went.

Dealing with false SPAM filtering is an issue which has been under discussion by the SUs for a while.  The advice fed back is that these issues should now be reported to the call desk.  If you get a non-plus response, ask the agent to "check Albert" for new guidance notes.

[#3]

@Dalesman can you pop me over your username via private message and I will look into this for you

[#4]

Not much progress to report yet. As below, Help Desk has picked it up and offered to look into it. They have asked me to send over headers to help with diagnosis. I'm not clear what they mean and have asked for clarification - I would guess this means the meta data which shows the routing of the message. But how can I access headers for messages which I haven't received?

[#5]

And that indeed is a good fundamental question!

The best you are likely to be able to offer is date and approximate time you think the email was sent and the receiving address. You might know the senders address.

If you can ask the sending party if they can forward the delivery rejection email, it might hold helpful information.

[#6]

Thanks, yes, I could send times and approximate dates, receiving addresses etc. 
I can imagine that the headers of the delivery failure messages might help but one of senders of a known failed message was a rail company (won't get any help from them) and the other (a bike centre) has already gone out of their way and I wouldn't want to waste any more of their time. I asked the bike centre to send instead to my university email address, which I rarely look at because it has an auto-forward to Plusnet, which I know is working. The email reached the primary address and I can access it there, but Plusnet blocked the auto forward!
Presumably Plusnet is identifying certain words or characteristics in emails which it wrongly thinks are spam. It also seems to me that this is likely to be the tip of an iceberg, because in most cases you simply don't know what you haven't received. 

[#7]

Ah auto forward - that’s a whole different ball game!!!

If the sending party has applied strict SPF and the forwarding service has not implemented SRS then there is a marked risk of such emails being correctly marked as spam.

SPF specifies which SMTP servers are authorised to send emails on behalf of the sender.

SRS effectively says “I am forwarding this on behalf of the sender … who sent by a valid SMTP server”.

Without SRS in the forwarding service, the email will appear to have been sent by the sender using the forwarding services SMTP server … which is then not compliant with the SPF specifications.

It is complex space when intermediary players are involved. There again it could be just content. Thinking of which, is there an attachment to this / these emails? Elsewhere I’m aware of some forwarding services corrupting the headers on emails having attachments.

[#8]

That's a level of complication I wasn't aware of! 

The answer is yes (in the case of both blocked incoming emails which we are aware of) - they both contained attachments or links.

I think it may be relevant also that Transport for Wales mentioned they were aware of "a number of instances" where sending e-tickets to Plusnet addresses had failed.

I hope Plusnet take this seriously. I think I'd rather have no spam filtering at all than this happening.

[#9]

Most people are not aware and should not need to be.

Forwarded emails are a whole separate class of spam issues. Unfortunately users rarely mention that the rejected mail is being routed via an automatic forwarding service.

Email address A forwarding to address B is not the same as user at A forwarding to B.

[#10]

Thanks again, but let's not get hung up on the ONE email that was sent to my 'other' email address (which has auto-forwarding) so that I could have a chance to deal with it. I thought it was interesting that this one too was blocked by Plusnet, but perhaps that's not surprising, despite the other issues with forwarding which you mention. 

This isn't a forwarding issue - the other non-delivered emails were direct to our Plusnet accounts from two different suppliers.

[#11]

Just come across another example of incoming emails not getting through to us. This one's from Skipton Building Society: "We recently tried to contact you by email, however it appears that this was not delivered successfully".

[#12]

not sure if my issue is related to yours, but a client of mine who uses Microsoft 365 is trying to email someone with a plusnet address and any email that contains an attachment is getting bounced with the message 'Spam Message Rejected'.

So far it seems that emails without attachments are going through ok.

The attachments arnt very large, and are mostly .pdf and .docx files

[#13]

Are those emails being sent direct to the Plusnet email address or are they being passed through a third party which forwards to the Plusnet email address?

IIRC the issue I’m aware of relates to MS Office attachments which have passed through certain email forwarding services. I’ll post a link laters.

[#14]

The emails are passing through Mimecast email security

[#15]

The cases I'm aware of do contain attachments (e.g. rail tickets) or links to websites.