I recently found that they allow email sender spoofing. I am in discussion with them to determine the details but so far the facts are my address was spoofed and they said everything is working as intended. I did not expect this, especially given this provider's reputation. I'm surprised, shocked, and upset.

My question: is it unreasonable of me to expect my email provider does not allow email sender fraud?

Edit: I appreciate the attention and I'm sorry I was not specific.

The provider accepted and delivered a message that originated outside of their domain where the sender and recipient is in their domain.

In other words, provider is Example.com, my address is tim@example.com, they delivered a message from outside of their network that had tim@example.com as sender and recipient.