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Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

FIXED
DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

Been using PlusNet for a couple of decades. Email from home office all fine.

Mobile (S10) has stopped sending emails saying that it cannot authenticate. Receives fine. Send fine over WiFi. Just mobile data connection fails.

Uninstalled/reinstalled Samsung mail app has no effect.

 

13 REPLIES 13
MisterW
Superuser
Superuser
Posts: 11,140
Thanks: 3,415
Fixes: 260
Registered: ‎30-07-2007

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

Fix

You'll need to use SMTP authentication to send email on a mobile connection https://www.plus.net/help/email-guides/how-to-set-up-plusnet-email/

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

Hi, thanks for the feedback.

I do and it hasn't changed for a long time. Incoming works fine, its just the relay server that does not like me.

 

DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

How can I "un-fix" this tread. As it isn't.

 

I have now tried Gmail and get the same issue.

MisterW
Superuser
Superuser
Posts: 11,140
Thanks: 3,415
Fixes: 260
Registered: ‎30-07-2007

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

In that case it could well be that the IP address you've been allocated on the mobile connection has been marked as 'suspect' due to activity performed by a previous user. If that's the case it usually sorts itself out in 24 hours.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

The issue has been going on for about 4 weeks and the phone gets switched off each night, so I'd expect varying IPs.

It would be good for PlusNet to be able to look at their logs and says why the authentication is failing.

MisterW
Superuser
Superuser
Posts: 11,140
Thanks: 3,415
Fixes: 260
Registered: ‎30-07-2007

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

The PlusNet servers do return an error code back to the email client, indicating what the error was. The problem is that many email clients (particularly mobile ones) don't pass that on , they just report authentication failed.

Are you using the Three network by any chance ? They use CGNAT so even though you are allocated a different IP , its a private IP. The connection to the mail server is still seen as being from the single public IP shared by many customers. If that IP gets a poor reputation then your disconnecting and reconnecting will not help.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

I am using three mobile. I have just checked my IP and then switched off and on again. Following which I had a completely different IP on a different class B subnet.

 

 

MisterW
Superuser
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Posts: 11,140
Thanks: 3,415
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Registered: ‎30-07-2007

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

This thread https://community.plus.net/t5/Email/535-authentication-rejected-as-source-IP-has-a-poor-reputation/t... showed a similar problem with a Three mobile IP

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

I will pass on these thoughts to Three.

Though as the connection does try and authenticate, I would have assumed that PlusNet would either trust their customer or tell them that they are being blocked.

Townman
Superuser
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Registered: ‎22-08-2007

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

Plusnet does indicate the reason for the non-connection ... but most email programs will not discern one 535 error from another.

If you can run TELNET on your S10, you could try this, ignoring the references to Win10 configuration.

Test SMTP authentication

Email programs often report username / password error for issues not actually related to those being wrong, but for other connectivity issues. Such can be very frustrating when you are convinced that they are correct. Testing SMTP authentication through a command line interface can deliver a more precise error message. The following describes how to do this using TELNET.

This is not difficult, but you need the following resources which might be unfamiliar...

  1. TELNET - this might need installing as an additional option, for Windows see enabling TELNET.
  2. A code64 encoder / decoder such as this.

You can use TELNET to communicate direct with the SMTP server as follows...

Open the code64 encoder in a web browser and leave ready for use in the following steps.

Launch a windows command line window (DOS window) - press windows-key+R - type CMD into the run box - click OK

Enter...

telnet relay.plus.net 587

Press enter. Note if you use one of the other brand email services, use the appropriate SMTP server name for that brand. In response to SMTP server I'm here message, say 'HELLO'...

EHLO relay.plus.net

The SMTP server will then report what it can do after which tell the server you wish to authenticate...

AUTH login

The server should return the following, which is a base64 encoded string that requires your username:

334 VXNlcm5hbWU6

Use the code64 encoder to encode your username and paste it into the telnet window and press enter. For example:

bXl1c2VybmFtZQ==

The server should return the following, which is a base64 encoded string that requires your password:

334 UGFzc3dvcmQ6

Paste the base64 encoded password for the username. For example:

bXlwYXNzd29yZA==

The server will then report success or failure, any failure message should clearly indicate the reason for the failure. If the reason for the failure is not clear, please report back the message.

Close the SMTP / TELNET session by entering

quit

The session should look something similar to the below wherein your input is in bold...

220 avasout03 smtp relay.plus.net
EHLO relay.plus.net
250-avasout03 hello [your IP address], pleased to meet you
250-HELP
250-AUTH LOGIN PLAIN
250-SIZE 104857600
250-PIPELINING
250-8BITMIME
250-STARTTLS
250 OK
AUTH LOGIN
334 VXNlcm5hbWU6
bXl1c2VybmFtZQ==
334 UGFzc3dvcmQ6
bXlwYXNzd29yZA==
235 ... authentication succeeded
quit
221 avasout03 smtp closing connection
Connection to host lost.

Here are some examples of failure responses...

535 ...authentication rejected [as username / password is wrong]
535 ...authentication rejected as source IP has a poor reputation

 

Note, you can remove the fix yourself.  Just go to the post options on the post you marked as "this fixed it for me" and select unfixed.

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DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

Been doing some more testing.

If the "send" fails I can turn off and on the phone and it then works for a while, but eventually starts failing again.

Townman
Superuser
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Registered: ‎22-08-2007

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

If that is over 3/4G then that is down to having been assigned a compromised IP address. Note that mobile IP addresses can be changing quite frequently. Suggest to check the mobile IP address from time to time.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

DonC
Newbie
Posts: 8
Registered: ‎28-08-2020

Re: Samsung S10 email stopped being sent to plusnet server, works fine with WiFi

Thanks, I used to do this all the time when I supported Unix systems 20-30 years ago. Did not think about it with android.

 

In typical fashion the connections been working all of today!