Unable to send invoices by email

We are unable to send invoices and recieve the attached error. We are using a GMAIL account with the below settings as instructed in the tutorals but keep recieeving an error when trying to send out invoices. We have also tried 2 step verification with an app password, that doesnt work either. we have also created and tried with a yahoo account but that just times out. Does anyone know the corec settings for us to use our gmail account to send out our invoices.

Settings used:

Authentication enabled
Gmail Username
Gmail Password
Port 587
less secure apps enabled in gmail

What version of manager are you using (SSL manual setting was disabled long ago)? On what operating system?

The Manager Version is 18.9.2 and the windows operating system is Windows 8.1 single language

That’s more than a year out of date so hundreds of versions behind. You will need to update see here https://www.manager.io/download/

Thank you for your response, as we are just the IT guys can the update just be installed over the current installation without data loss? What is the best method to update without losing the clients data?

@ittech, please keep your advertisements off the forum. See https://forum.manager.io/faq. Your posts were edited to remove them. This is because you responded by email.

you have not mentioned what edition of Manager you are using (Desktop or Server).
anyway, updating Manager is the exact same procedure as installing.
read the guide regarding the same.

The problem has been resolved with the new update. Thank you very much.