Outbound Email to regular correspondent suddenly rejected "due to spam or virus"

[#1]

Hello, with my first post here.

Midway through a conversation with people at a firm I've worked with for several years, my email replies to them are blocked by an "unable to send due to spam or virus" message, as in the screenshot attached.

Sometimes in the past their logo has triggered this, and deleting it makes all well. Now if even the tiniest shred of blue line from where I deleted their message triggers it, and my only way out is to create a brand new message, copying in my text, their addresses, etc, and sending as new. Which means I lose the thread of the conversation.

Since it's a seasonal thing where I'm discussing different events with 4 or 5 of them at once this is a real nuisance! It's possible they've been infected with something, I suppose, but I alerted them to this, and they've not found any problem that I know of yet with any of their other correspondents.
Any help most gratefully received, please.

Thanks,

Richard

[#2]

Hi Richard, sorry to see this is an issue. If new messages from you get through fine the issue must be on there side if it's only happening when you respond to their replies so it does look like something they'd need to look at for you. 

[#3]

Thanks - this reinforces what I felt must be the case.

I've batted it back to them. So it's not solved yet, but hopefully we'll make some progress.

Best wishes,

Richard

[#4]

@adamwalker

If this error is being reported during the send action, then this is a Plusnet SMTP generated event. It suggests that there is something in the body of the email being replied to which is triggering PlusNET’s anti-spam measures.

As a means of diagnosing the issue, I suggest sending replies in plain text, rather than html and see if it makes any difference.

[#5]

Thanks Adam.

Yes, I'm sure it's something in the body of their emails. If I copy all their text, but carefully delete their logo, and even the smallest shred of that blue line down the side of messages in threads, it sends fine. Otherwise, with every member of that company, it's rejected. Which is a pain when replying to a sudden flurry of work offers from a nice friendly company!

I alerted them to it, and their reply was: "I’ve passed your note onto our Digital team and it appears our web server is rejecting your mail because it suspects something malicious – unfortunately there’s not a lot we can do about this and the error message suggests it’s a problem your end."

which means that at present my only hope is that something re-sets itself soon, unless there's anything else on offer.

I'm not greatly high-tech, but follow basic instructions 🙂

I'm running Mozilla Thunderbird on Linux Ubuntu Operating System, if that's relevant.

Thanks again,

Richard

[#6]

Whlist you see this as being a problem with a bit of their branding being contained within the email being replied to, I would suspect that said graphic has a link to something thought to be suspect.  Deleting the "thin blue line" must be deleting more than the graphic - possibly a hidden link.  If the theiry is correct, changung the reply to text only should eliminate the tissue.

Whatever, the problem remains that anti-spam / anti-pishing measures have cause to be concerned about THEIR content!!

[#7]

Thanks, and I'm very inclined to agree with you - I'm not highly technical, but logic suggests it's their problem indeed!

Meanwhile in my ignorance, I can't find how I change replies to "text only" .

Thunderbird preferences tab brings up Compostion options, where under a headline HTML I have options to adjust fonts etc, but doesn't seem to give an option for text only replies. Sorry for density on my part!

Best wishes,

Richard

[#8]

Sorry, I am not familiar with the Thunderbird client, others here might be able to assist on that precise point.  However in generall all email clinets provide the means of setting the format both globally (default) and on a specific email.  Usually uner "options" or "format".

[#9 · Accepted solution]

Details are here http://kb.mozillazine.org/Plain_text_e-mail_%28Thunderbird%29

[#10]

Great, thank you. As simple as pressing Shift at the same time as "Reply" - even I can cope with that!

What excellent quick help.

Best wishes to all,

Richard