Setting up email Notification on Azure DevOps
AFAIK, Azure devops does not support add attachment in email Notification directly.
As workaround, we could use a powershell script to get test results with REST API then send emails:
To get test results with RESI API Releases - Get Task Log:
GET https://vsrm.dev.azure.com/{organization}/{project}/_apis/release/releases/{releaseId}/environments/{environmentId}/deployPhases/{releaseDeployPhaseId}/tasks/{taskId}/logs?api-version=5.0-preview.2
Then use powershell scripts to read the details of the test result file (.trx) and create a formatted email message to sent to the defined recipients:
You could check this thread Send Test Result Email After Running Automated Tests with Release Management for some details.
Hope this helps.