If you have created an eM Client startup password and have Windows then see the following post from @Gary how to clear the startup password in the following thread…
Now if you have forgotten your email account password “and there is no password option in any eM Client accounts tabs” to type in a new password, that usually means your account is a passwordless modern OAuth / OAuth2 token login where you just clicked allow / ok instead of a password when setting up your account.
So if you can access your email via the
123-reg website ok, but cannot enter a password, in eM Client accounts due to no password field, then in that case you would go to “Menu / Accounts” and click on your account and remove and readd your account via the automatic account wizard at the top. If you then have an IMAP, Exchange, Office 365 or iCloud account all your emails etc will come back from the server shortly after eM Client connects.
Note: If you do remove and readd your email account make a manual backup first via “Menu / Backup” just incase you need to restore for any reason. You can see when the backup is complete in Show Operations via clicking the drop-down on the right of Refresh top left.