Sending emails fails using WiFi connections not my own

[#1]

Sending emails works fine from my Android phone (Samsung Galaxy A42 5G) when I use my own WiFi connection.

But recently, while in Spain, sending emails failed when using the WiFi connection of holiday lets, restaurants, etc.  (Curiously, using Data seemed to work.)

On my return to the UK, the same thing happened when I tried to use the WiFi at Bournemouth Airport.

The reported failure was "Couldn't authenticate account.  The password or authentication method may be incorrect.  Check your outgoing server settings and try again."

I did check them and  there is nothing wrong with them.  If they weren't correct, I shouldn't be able to send emails using my own WiFi.

Can anyone suggest what might be going on?

[#2]

I should add that switching off VPN makes no difference.

[#3]

Works at home naturally, but settings need changing when you're using someone other than PN to connect; use SEARCH box on forum to get correct settings.

[#4]

@AndrewGood 

If they weren't correct, I shouldn't be able to send emails using my own WiFi.

Yes , you would. There is no need to authenticate when sending from a Plusnet connection. When sending from a non-plusnet connection you need to set authentication on the outgoing server. Use the same credentials as used for incoming. See the help pages here https://www.plus.net/help/email-guides/how-to-set-up-plusnet-email/

[#5]

I checked and Authentication is set to ON.

[#6]

I have security type SSL and port 465, which is what PlusNet recommend when you don't have the STARTTLS option available.

[#7]

The smtp server also uses an 'IP reputation' score. When on public or foreign networks it can often reject a connection due to the reputation of the IP from which connection is attempted. Although, in this case, a different error code is sent to the email client, most don't differentiate and just output the 'authentication details incorrect' message.

[#8]

@Gel

If set up properly / fully there is no need to change anything when off network. Set up only in part - no authentication on the outgoing server because it’s not mandatory when on the network - can give rise to this symptom. However other conditions will give rise to the same symptoms with authentication set, as is happening here.

[#9]

Do you know roughly what date/time you got the error? Not sure we'll have any logs but I can check if I know when you had the error and see if it says why it failed.

[#10]

I tried numerous times while in Spain.  One email got through on 3 December at 10:00 (not sure whether that's UK or Spanish time) but all subsequent emails failed. I tried endless times between then and 7 December (the last day of my holiday) to send test emails to myself, but no attempt succeeded.  I'm afraid I can't give the times I sent the emails, as I've since deleted them from my mailbox.

[#11]

The dates are good enough, I can see lots of rejections in the logs with 2 reasons:

info="SMTP Auth message blocked as sending IP is listed on Spamhaus Zen"

info="SMTP Auth message blocked as sending IP is listed as poor on CSI"

Checking the IP addresses you were using on Spamhaus https://check.spamhaus.org/ gives the following reasons:

First IP address:

1. eXploits Blocklist (XBL) - Why was this IP address listed?

The machine using this IP is infected with malware, or is sharing a connection with an infected device.

As a result, this IP is listed in the 

eXploits Blocklist (XBL)

Click on More Info to see if you can request a delisting from this blocklist. This will also display any further information we have relating to this listing.

 Second IP address:

1. Spamhaus Blocklist (SBL) - Why is this resource address listed?

This IP or range has been observed to be involved in at least one of the following activities; sending spam, snowshoe spamming, hijacked IP space, or associated with spam services (web, dns, etc) or bulletproof hosting. For more information, read Spamhaus' listing criteria for SBL inclusion.

As a result, this IP is listed in the 

Spamhaus Blocklist (SBL)

TL;DR: We blocked you from sending emails while using these 2 IP address because they've been reporting as sending spam or having malware, we have no way of knowing if it's a legitimate Plusnet customer on holiday or someone has compromised your account and trying to send spam via our servers from Spain so the system errs on the side of caution and will block. Webmail would still work I think as that does different checks. Not sure whether we can reject with a better error message as that might be what the mail client interprets it as regardless of what we send as rejection reason.

[#12]

Thank you for looking into this.  It looks like there's been some funny-business going on.

I was worried that there might be malware on my phone, but I have AVG AntiVirus on my phone, so hopefully the infected phone will be someone else's who's used that IP.

Would you agree that it's likely there's nothing wrong with my settings?  And that it's the poor reputation of those IP addresses that's likely to have been the cause of my problems?

[#13 · Accepted solution]

Absolutely.

If your phone works somewhere / sometimes the issue is not your settings. Unfortunately regardless of the detailed connection rejection message detail (as hinted at by @dave) the majority of email clients will report a username / password failure. All in all very unhelpful.

There is a fair possibility that the “bad actor” on the IP address is not you but some other party who was allocated the dynamic IP address previously.

Some ISPs share a public IP address across multiple end user connections. Dropping off network for a while / using a different WiFi or roaming provider might improve your experience by obtaining a clean dynamic IP address.

[#14]

If the places it was failing was a restaurant with an open WiFi hotspot or where the WiFi password was displayed behind the bar or a an apartment with shared WiFi it's likely that someone's just used it to spam from until it stopped working and left it. Or if it's a dynamic IP address, which most IPs are these days, it could be the person who had the IP last.

I'd highly dought it was you as these lists don't work that fast, it would've worked OK to start with if it was and likely your home IP address would be on the same list. It's 99.99% going to be someone else and as I say more than likely than not it wasn't even done at the places you were using.

Your settings will be fine as it sounds like you sent from the mobile networks and others OK it's just bad luck that 2 of the places you used were on spam lists.