problems sending email , receives ok

[#1]

in the past couple of weeks I've had issues sending email from my plusnet email it receives ok but comes up with a username password error when trying to send , I'm not with plusnet broadband and haven't been for years but kept email

emails won't send from home pc through outlook or through my iPhone (although sometime it gores later from my phone )

nothing has changed settings are all the same 

I'm hoping someone can help

many thanks 

[#2]

When did this work last?

I would suspect that you have acquired a 'dirty' IP address.  Email clients are not very good at providing precise error messages when the connection to the SMTP server fails: a lazy "password error" is used to cover many sins.

Can you send if you use Webmail?  That would verify that the account is fully operational.

Determining the exact cause of the issue, needs some precise diagnostics - the following looks a lot more complex than it really is ... give it a try and see what the precise issue is.  My money is on an issue with your current ISP.

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
535 Too many SMTP auth failures. Please try again later.

[#3]

thanks for coming back to me , i used my VPN and it worked , I assume my IP is blacklisted how do I go about sorting it I use BT broadband at the mo 

thanks 

[#4]

That's difficult!

Take a look here: https://mxtoolbox.com/

Who is black listing it and why?

Some of the black listings last only 24-48 hours and it might resolve itself.  Some black listings need proactive removal - you might be able to make the request, some circumstances require the ISP to make the request.

Potentially the easiest approach would be to switch the router off for 2 hours and hope when you switch it back on, you are allocated a different IP address.

[#5]

ideal , I'll turn the router off and keep my fingers crossed

thanks for your help