Still can't send emails

From what you’ve mentioned, it sounds like you may have missed making changes to the firewall within your Linode. Even after restrictions have been lifted from our side, you will still need to open the mailing ports from within your Linode via the firewall configuration before you can start sending mail. This will need to be done using an SSH terminal or the Lish console from within the Linode Manager.

You can open these ports by running a few commands but in the end, the exact command to run will depend on your Linode's distribution and your firewall. The following post covers a few different ways to open a port on your Linode so I’d start here:

---> How do I open a port in my Linode's firewall?

Once you've made the necessary changes, you can confirm which ports are being used with a command like:

netstat -ltp

This (plus other ways to check on your Linode's ports) is covered in more detail in the following guide:

---> Linode Documentation: How to Check Which Ports Are in Use on Your Linux System

Note for while you're working on this:
The default mailing ports for most mailing services are 25, 465, 587.