Does my authentication password for em client need to match my password for my optonline email address.
Yes most users do use the same mail server password for incoming and outgoing mail.
So if you cannot send mail and getting a password error, then yes could be you don’t have the same or correct password as your Incoming mail server, depending on if you use the same mail server for sending & receiving mail.
Some users though use different SMTP mail servers to send mail “for various reasons” so would have a different password to send mail than their incoming mail server.
The other reason you mail not be able to send mail is if you have the wrong SMTP mail server setting so would need more information.
What version of eM Client are you using, and do you have Windows or Mac ?
Do you use the same mail server for sending and receiving mail or different ?
Also what are your eM Client Mail Account settings for receiving and sending mail ?
Note:- Blank out your account name and password.