For latest updates on HVE, please see this post as well as this post.
Today we’re thrilled to announce the public preview of High Volume Email (HVE) for Microsoft 365. HVE is a new service designed...
Updated May 06, 2025
Version 5.0
Blog Post
I really wouldn't get agitated about the 10 external recipients per minute limit. All software has limitations and some are documented and some are not. HVE is designed for internal messaging (with some extrenal capabilities). Apart from the 100,000 internal recipients daily, there's nothing to stop you sending large quantities of internal email daily... and that's what HVE is designed to do because Microsoft wants HVE to replace on-premises servers used by devices and applications to send email. I certainly have not found it difficult to stay within the limitations once they became apparent.
If you want a different solution that can handle external recipients better, consider ECS https://practical365.com/ecs-email-communication-services/. ECS is also based on Exchange Online, but it has a different target audience and does not support the basic authentication needed to service many devices and applications.