Tell me how you can set up “beautiful” notifications about the arrival of a new ad.
I tried to send mailing messages using MailPoet
A user with the “Seller” role posts a new ad.
All users with the Buyer role receive emails from the Template with a short description of the ad.
Is it possible to do this through third party applications?
What plugins can HivePress triggers see?
Sure, please check the latest reply in this topic https://hivepress.io/support/topic/emails-and-security/#post-10746 You can override the email template (and add any HTML email template you like). Adding custom tokens (like listing descriptions) would require extra customizations, at the moment the Search Alerts extension just sends the search results URL (so users can view recently added listings that match their search criteria).