I cannot send or receive emails since the latest update. I get an authentication error. I can post the error if I can work out how to do it. 
Hi Christine, what version of eM Client are you currently using and what mail service are you using with eM Client?
Thank you,
Paul.
Hello
I am using the latest version and it is rubbish. Mail service is talk talk but whenever I do the same settings on a different mail client like outlook 2007 it works. So it is your latest download that is failing. I have re added passwords and such.
Hi Christine, can you please tell me the exact version from Help > About?
Are there any errors displayed while trying to send/receive (except the authentication issue)?
Are you using any firewall/proxy or antivirus software on your computer?
Thank you,
Paul.
The version I am using is 6.0.21040.0
I am using Avast free anti virus and I have turned it off but still do not have any joy. That version is 2014.9.0.2021
I should add that this problem occurred when I changed my password, it is like emclient just will not realise that and maybe it is sending the old password. I dont know. No errors only the authentication issue
I also have windows firewall
I am a new emclient user but have been a gmail user for many years and was until today using Zimbra. I am running the same emclient version as Christine and can receive email from gmail but I cannot send. If I go to the diagnostics tab and click Diagnose it IMAP goes green very quickly SMTP “Faied”. I then click on Fix and it goes through a few iterations and then says Fixed and I receive a test email. The headers on the test email show that it has indeed gone through the gmail servers.
I then go back to the outbox and click send and receive and the SMTP process still fails.
Would be nice to get this working as the client looks good.
I turned on the logging for the SMTP service and I can see this line:
13:05:25 [email protected] [SMTP] MailExceptions.SocketException: Connect failed with reason:
13:05:25 “A socket operation was attempted to an unreachable network [2404:6800:4008:c03::6c]:587”
The SMTP process has bound to my IPv6 interface. Unfortunately our network does not yet support IPv6. It is on the ToDo list 
Hi John, unfortunately this might be a matter of your server settings. You should be able to setup your account to not use the IPv6 protocol.
Hope this helps,
Paul.
Hi Christine, how did you change your password, did you change the password on the mail server and in eM Client as well? What mail service are you using?
Can you try to setup the account again using your new password or make sure you’ve updated your new password in eM Client?
Thank you,
Paul.
Any pointers to where that setting might be? I assume you mean the account setup in emclient? I have to ask the question why is only the SMTP part of the emclient using IPv6? Also I didn’t have this problem with Zimbra so it is not a GMail account setting or a PC setting.
Changing the emclient SMTP setup to use port 465 and policy SSL/TLS on Legacy port has fixed this issue. Hope this helps others.
Hi John, glad you were able to resolve the issue, please let us know if you come across any other issues or questions, we’ll be happy to help.
Thank you,
Paul.
Hi Paul
someone sabotaged my post and you have not helped me. I still cannot send or receive emails, if you cat sort this out then I will just have to uninstall it.
Hi Christine,
I think you’ve not yet answered the questions Paul has asked you:
Hi Christine, how did you change your password, did you change the password on the mail server and in eM Client as well? What mail service are you using?
Can you try to setup the account again using your new password or make sure you’ve updated your new password in eM Client?
Can you please answer these questions? It might help us in helping you.
Hi
I did answer, dont know what happened to the post. I changed my password on the mail server and then I uninstalled EMCLient as it would not work when I changed the password there. I then reinstalled it and tried again with all new accounts but the same problems. I am using talktalk.net UK. I have set up the account many times but it keeps going back to the old one I am sure that is what is happening, it is like EMClient is just not recognising the new password. This is a problem.
Hi again Christine, are you seeing any error messages from the application? What version of eM Client are you currently using on your computer, can you check for the exact version number in Help > About?
Are you using any security software on your computer?
Thank you,
Paul.
AS STATED ABOVE;
The version I am using is 6.0.21040.0
I am using Avast free anti virus and I have turned it off but still do not have any joy. That version is 2014.9.0.2021
I should add that this problem occurred when I changed my password, it is like emclient just will not realise that and maybe it is sending the old password. I dont know. No errors only the authentication issue
I also have windows firewall
Hello anyone?
Hello anyone
Changing the emclient SMTP setup to use port 465 and policy SSL/TLS on Legacy port has fixed this issue. Hope this helps others.
It did help me resolving my issue!! Thank you much John!!
I tried that but no it does not work