Email / webmail issues

lesbailey — Fri, 31 Dec 2021 22:47:54 GMT

I have 2 email addresses on my plusnet account, the main account and an additional mailbox. I have have had ongoing issues with the additional mailbox over the past 3 or 4 months. Firstly my Microsoft Office Outlook stopped sending emails so I had to resort to using my Iphone and webmail. Both of these have now stopped sending leaving me with no facility to send emails. No settings have been changed and I am still receiving emails. Any help appreciated.

Just to add, when trying to send using webmail I get a 'SMTP Error (535): Authentication failed' message.

Re: Email / webmail issues

Townman — Sat, 01 Jan 2022 10:03:24 GMT

Hello,

A warm welcome to the forums.

Are you connecting to the internet using PlusNET as your broadband supplier?

Are you using a VPN?

Re: Email / webmail issues

lesbailey — Sat, 01 Jan 2022 10:27:57 GMT

Hi, thanks.

I have had Sky fibre broadband for the past 12 months. I am not using a VPN.

Re: Email / webmail issues

Townman — Sat, 01 Jan 2022 11:31:07 GMT

I thought as much... you are not a Plusnet subscriber whilst using a retained free email service.

The security vetting of third party network connections is somewhat more stringent so as to protect the integrity of Plusnet's email relay services. This is very standard practice. I would suspect that your Sky IP address has been marked suspect. Unfortunately most email applications cannot discern the detail of 535 error states - they are all reported as "password errors" when they are probably not. You need to do some digging to find out what the real issue is.

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...

TELNET - this might need installing as an additional option, for Windows see enabling TELNET.
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
535 Too many SMTP auth failures. Please try again later.

I suspect that you will get the "source IP has a poor reputation" response. Once that has been verified, then the issue needs to be reported to Sky so that they can clean up the reputation of their IP addresses.

You can find your IP address here - What Is My IP? Quickly See My IP Address and My IP Location - and you can see if it is blacklisted here - IP Address Blacklist Check - WhatIsMyIP.com®

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