I believe you are using V15.5
Go to Settings > Email
Check and confirm that all the entries are correct.
Once you have confirmed everything is correct, click on "Test".
You will receive a confirmation about whether everything is working fine or not.
If it isn't working, follow this link and configure it correctly. https://www.3cx.com/blog/docs/gmail-mail-server/
Here the email account used is Gmail, if you are using your official email, then there is no need to configure 2nd part mentioned in the post.
As techdummy suggested you should first check and verify that the PBX is able to send notification emails. Follow the guides and if further assistance is needed we are more than happy to help.
Once you make sure that your email is working, navigate to the Extensions Tab of the PBX and make sure that your extension has a valid email address configured. Then select it and click on the welcome email button on the menu above the extensions.