Yes, but consider your internal risk analysis.
The email you have meets the technical requirements of HIPAA. The only requirement is that the email is encrypted while it is being sent, which is how our server is configured.
However...
Once received, the email is just like any other - anyone with access can read it. While this meets HIPAA guidelines - it may be relatively easy for another person to gain access. Whether a family member in the household, or the theft of a laptop - there are a number of scenarios that might make the email available to someone other than the intended recipient.
We recommend that each organization perform its own risk analysis to determine what is actually appropriate for them, based on their business practices, to minimize their risk.