Note: Make sure you are using either Google Chrome or Firefox during the installation process.
Create your email signature on NEWOLDSTAMP.com and follow these simple steps to install it in Roundcube.
After you finish creating your email signature, click Save and Install button under the signature preview.
Or, if you have saved your signature priorly, hover over your signature on the dashboard and click Use button.
Select the option Other in the list of email clients.
Choose the HTML tab and copy the HTML source code by clicking Copy and proceed button.
Open your Roundcube webmail client.
Note: Make sure you use your full email address and password when logging into webmail (not your cPanel username and password).
Once you've logged in, you will be presented with three webmail options. You can also verify the correct email account has been entered by checking the upper-right corner.
Click on Settings in the top right-hand corner, then click on Identities.
Note: There is usually a default identity already in place, but you can also create a new one by clicking on the plus sign at the bottom of the identities column. If you are creating a new identity, then fill in the information for that identity and make sure it's correct.
Next, click on HTML Signature to add the HTML toolbar in the Signature input field.
Then click on HTML in the toolbar of the editor and then add your HTML source code.
Click on Update to save your HTML code.
Preview your HTML signature and make sure it appears the way you want it, then click on Save to save your signature.
Also, you can check this guide for more screenshots.
Congratulations! Now you will see your new signature on every message you send with Roundcube.