404 - Execution of authentication request unexpected result - 404 ()

Significant sync issue.  Email coming thru - but calendar not syncing with other devices at all – and I expect this error above is related to calendar.  Have had this problem for a couple of weeks.  About to uninstall Em Client and move to another app on my desktop, as the errors are continuous and block my use of the email – I have to continue to click them off.  Can’t find a fix.  It’s only on the Gmail account.

Hello Carol, can you please make a screenshot of the error or copy the content of the Log tab from Operations and submit it to us here for more information. What version of eM Client are you currently using on your computer, can you please check the exact release number in Help > About?

We came across this issue with a 404 error on Google’s calendar and contacts services, however came up with a workaround to re-setup the account in eM Client, this apparently solved the issue for most users experiencing this.

Can you please try to re-setup your account in eM Client and check if the issue persists?

Thank you,

Having the same problem, also with gmail account

If I re setup the account I’ll lose all calendar changes, isn’t there another fix?

Hello Frederik, unfortunately there’s no other workaround for the issue, the issue has been caused by Google disabling some of the older API’s and resetting up the account can clear the stored data from the server. You can disable the account in eM Client and copy your calendar changes over once you setup the account again.

Hope this helps,

In the meantime this error is solved, what I did was to remove my unimportant messages from this account, and to forward the remaining (important) ones to another account I already had at Gmail, just in case. After that, I deleted this account having problems within EMClient, restarted the application and set it up again with the same parameters or values. To my surprise all my mail was still there. No more errors. I hope this helps.

Glad it works, please make sure to let us know if you come across this or any other issues or questions about the application, we’ll be happy to help.


I’m getting the same error. Disabling and setting up account again hasn’t worked for me

In Tools, Accounts, once your account is selected, then in the Diagnose tab, have you fixed the incoming IMAP or POP and outgoing SMTP ports by clicking on Diagnose? Try this, it may work for you. Best regards, Fernando

Diagnose finds no problems and test email comes through ok, but I get “Synchronising folder list failed with an error: Execution of authentication request returned an unexpected result :404”. I also get a similar message for my contacts folder, and my calendar has stopped syncing also.

Hello Vinnie, what version of eM Client are you currently using on your computer, can you please check the exact release number in Help > About?

Make sure you’re using the latest release, 6.0.22465.0, re-setup the account and check if the issue persists after updating.


I’m still on version 5. Not happy that the only way I can restore functionality to the program is to pay for an upgrade.

Hello Vinnie, this is unfortunately unpredictable, version 5 has been developed on certain standards that have been current while it was developed and released, but unfortunately Google has shutdown support for some of the features eM Client 5 was using and it is no longer possible to authenticate with the server using this release.

We’ve updated the current release, eM Client 6, for compatibility with these changes, but unfortunately it is not possible for us to include these new implementations in the older releases.

Hope you understand,

I understand that you can’t implement the change in an older release. My problem is with being asked to pay a second time to get back a  function that I’ve already paid for.

Hello Vinnie, I’m sorry if this has caused any inconvenience to you, but unfortunately the feature that has been included in eM Client 5 that allowed you to synchronise your calendars/contacts with Gmail in this release, is no longer supported by Gmail. The new authentication method - OAuth, is a different authentication process and the feature was additionally implemented into the current release. It is essentially a completely different feature and is considered to be a new standard for authentication.


Since at first it is not eM Client’s fault neither is it Vinnie’s fault, why eM Client doesn’t make him an offer? Should he stay for ever having problems unless he pays for an upgrade?  Too many people in the same situation? Just thinking aloud…

Hello Fernando, unfortunately the only available solution is upgrade to a later release as eM Client 5 is no longer supported.

You should also be able to use your account as long as you need since it’s only the calendar and contacts services that are unable to sync using the old authentication option, IMAP and SMTP services should still be able to authenticate using regular password authentication. In order to setup your Gmail account as IMAP and SMTP only, use the manual setup in Tools > Accounts > New Account > Mail > ‘Other’.

You can purchase a one time upgrade if you need to upgrade your PRO license using this offer, or purchase lifetime upgrades to avoid any similar issues in the future and have the latest available version always available for update.

Hope this helps,

Having the same issue on V6, Windows 10.  Here’s the issue though.  I originally installed it an everything was fine.  Then I remembered that I was supposed to install it on a separate drive from C: so I uninstalled, made the changes to Windows to set the default install location, reinstalled and I start getting this problem.  All within an hour or two.  Ideas?

Hello, please update your eM Client to this release, 6.0.22930.0 and check if the issue persists, if you continue to experience this issue please try to re-setup your account in eM Client.


I have the same problem.  Always getting 404 error message.  I deleted account and added it again: no help.
uninstalled emClient and installed again I saw my gmail account was still present: no help.

How can I delete all of emClient and have a clean install?

I have 2 laptops (all other gmail accounts), 1 laptop has no problem and other always 404 errors.
Both have latest emClient, Win10