535 ...authentication rejected as source IP has a poor reputation

[#1]

I am getting this message above from Plusnet's outgoing email server (relay.plus.net), and hence I cannot send emails.

I have an email-only Plusnet account, as I have to use Three 4G mobile for my broadband at home, as I could only get <1Mbps via ADSL, and there is no cable nor fibre here.  Plusnet clearly regard Three 4G mobile as potential spammers, and occasionally (it has happened three/four times now) they give me this message when I try and send email:

"535 ...authentication rejected as source IP has a poor reputation"

I can prove this is exactly the problem, by changing the SIM in my home broadband router to a SIM from a DIFFERENT network provider, and the relay.plus.net response changes back immediately to normal - i.e. OK - and I can send email again.

Is there any way of asking Plusnet NOT to treat Three as a spammer like this? Please?

[#2]

In answer to your final question, @mooblie , the answer is unfortunately 'no'. To protect its own platform (and customers), Plusnet use the 'Cloudmark' anti-spam technology, and unfortunately all mobile networks IPs - not just Three - tend to be used inappropriately by indiscriminate individuals for spamming &c.

Have a read at this topic for a more informed response: https://community.plus.net/t5/Email/Outgoing-email-not-working/m-p/1802922#M33947

[#3]

Thanks, John.  I feared as much.

It's a shame the Cloudmark system seems like such a blunt instrument. Does it ban IP addresses forevermore? Doesn't it know IP addresses get given out randomly, and users of any given IP address certainly can change over time? Should I be pushed to using a VPN (like real spammers) to avoid this issue? Is that what they want?

Also a shame Plusnet couldn't/don't implement something more appropriate for domestic users. I can think of simple alternatives - like max limits of, say, one email per minute? - or, say, fifty recipients per email?

If Plusnet cannot offer fixed cable/fibre links, then another solution would be if Plusnet Mobile offered unlimited-data SIMs for home use, like Three and other mobile operators have been doing for a couple of years now.

Are Plusnet staff likely to read here about this increasing email problem? or do anything about it?

[#4]

@mooblie Any 'commercial' product will seem like a 'blunt instrument' - they cannot be fiddled with by the users, and are set to cover normal behaviour patterns.

The 'reputation' of an IP is constantly monitored, and AFAIK, if it is seen to be operating 'within the rules' it will eventually be 'decriminalised'. Of course it 'knows' the IPs are randomly issued, but it doesn't know you are not a baddie until it has had time to analyse the behaviour. The use of VPNs wouldn't necessarily get you any further - those IPs can also be monitored and listed.

The only time that type of limit is used is where the system sees your IP as non-UK, so potentially, using a VPN could make it kick in as the IP you could get via a VPN may be from anywhere, even if you use a UK based service.

Plusnet Mobile is unlikely to do that as they are the 'cheap' brand of the BT stable, so a 'all bells and whistles' product is unlikely.

This is not an increasing problem - just strange that you and the OP in the linked post are having it at the same time, and TBH, these two are the only reported occurrences that I am aware of, and to be honest I doubt you will get a staff response - which is why I decided to pick this up.

[#5]

OK, thanks for your input again, John.

Not quite sure how best to deal with this now, as I suspect we will never get fibre/cable here and I am stuck with wireless broadband....

[#6]

@jab1  I've seen this problem 1st hand. Up until this year ( for obvious reasons ) we've normally spent a few weeks in Portugal in the winter. The house we rented had mobile broadband and intermittently ive seen the problem when the router has got a new IP. In my case I have access to the office VPN so have been able to get around it. As you say the problem usually goes away in a day or so as the ip reputation returns to normal.

[#7]

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@mooblie wrote:

OK, thanks for your input again, John.

Not quite sure how best to deal with this now, as I suspect we will never get fibre/cable here and I am stuck with wireless broadband....

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To be honest, @mooblie , you will just have to live with it - it shouldn't happen too often.

[#8]

Quote:

  "To be honest, @mooblie , you will just have to live with it - it shouldn't happen too often."

OK, three hours later: it's happened again! with a different SIM, different mobile network and different IP address. Same message: "535 ... poor reputation". Brilliant.

So... I'll start restarting my router to try and get issued with ANOTHER IP address? Not sure what else to try.

My sending email login is authenticated with my username/password.

Not a very workable system, this. 😞

Plusnet? Please!?

[#9]

You could always switch to - say - Gmail, and see how happy or otherwise they are with your IP - I'm afraid Plusnet won't risk their mail platform for this very isolated problem.

Authentication isn't the problem - the IP you are sending 'from' is.

[#10]

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@jab1 wrote:

Authentication isn't the problem - the IP you are sending 'from' is.

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I'm a little confused though as given that authentication is in place why should the reputation of the IP address matter all? Authentication proves who the sender is - and that they are a Plusnet customer - and so if the OP behaves badly Plusnet should just be blocking his access to the mail system. Blocking him on the grounds that someone at some point before him (when? years ago?) did something bad from that dynamic IP address just doesn't make sense - too high a risk of false positives. I think Plusnet have screwed up with this approach.

[#11]

@MJN As I understand it - and I could be wrong - mobile IPs are not 'exclusive', i.e. they are 'shared' and as you can't request a static IP on mobile networks AFAIK, they probably change as you move masts/areas.

Again, AFAIK, these 'blocks' are fairly transient and usually get reclassified as 'good' within a couple of days. I'm not saying any more as I haven't had need to research, so I'm only going on bits & pieces of information I have picked up along the way.

[#12]

Even if there is some automatic 'clean up' process then if it takes days that's far too long - I'm sure the OP would like his message sent before then! 🙂 As I said, authenticated mail submission should not be subject to reputation-based address checks like this - you either trust the sender based on who they are or you don't; it doesn't matter where they are connecting from. It's like arresting someone merely for walking through the bad part of town, even after positively IDing them and confirming them to be legitimate (and a valued paying customer to boot!). It sounds to me like some of their absolute anti-spam filtering rules for SMTP has been allowed to inadvertently spill over into the Submission side of the mail system where it likely causes more harm than good. That or they don't really care either way what the collateral damage is.

[#13]

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@jab1 wrote:

You could always switch to - say - Gmail, and see how happy or otherwise they are with your IP - I'm afraid Plusnet won't risk their mail platform for this very isolated problem.

Authentication isn't the problem - the IP you are sending 'from' is.

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I have to concur with MJN:

Authentication isn't the problem, but it SHOULD be the solution to this.

And: the IP I am sending from is NOT the problem - for it is clearly dynamic and temporary, and nothing to do with me.

And also - switching to Gmail is a bad solution - for I would have to change my email address, known to my large number of contacts.  Not very professional for me, and not very user-friendly of Plusnet to expect me to do that. 

I am CLEARLY an innocent victim here, being punished for inheriting an IP address previously abused. In what way is that my fault?

Not quite sure why you appear to be defending Plusnet here so vehemently, John, in the face of alternative solutions. We've all been in business - even software development - and we all know about the costs and timescales of technical solutions and the adverse impact of such situations on customer relations. But Plusnet have got this wrong at present.

[#14]

Maybe they're trying to nudge you towards Plusnet Mobile... 😉

[#15]

I would happily move to Plusnet Mobile, if only they did Unlimited Data SIM-only deals for £20pcm, like other operators.  Clearly those deals are intended for exactly this application: 4G mobile broadband at a fixed/home location.

You'd think the Plusnet marketing department would be onto this: to answer the Marketing Director's question at a strategy meeting: "What can we offer to customers who can't get fibre?" But no.