How to reset sensor after triggered?

I am loving learning templates, but have hit a wall on something probably simple. I have an IMAP Content sensor scraping gmail for email notifications of a new voicemail. It triggers a simple automation that announces through Alexa that there is a new voicemail. It works once - but it only detects the first email, after that, the sensor stays true. Restarting HA fixes the issue, but obviously that is inelegant, to say the least.

Is there any chance someone might be willing to help me learn to do this correctly? I have been struggling with it over the past few days, and it is driving me mad.

- platform: imap_email_content
  name: voicemail_alert
  port: 993
  scan_interval: 60
  folder: inbox
  username: !secret xxx_google_user
  password: !secret xxx_google_pass
    - [email protected]
  value_template: >-
   {% if 'New voicemail from' in subject %}
     New Voicemail
   {% else %}
     No Voicemail
   {% endif %}
alias: Phone - Voicemail Notification
  description: ''
  - platform: state
    entity_id: sensor.voicemail_alert
    to: New Voicemail
  condition: []
  - service: notify.alexa_media_all
      message: New Voicemail, New Voicemail
        type: tts
  mode: single

It will stay true as long as the email with the keywords is in your inbox. Try deleting or moving the email (then waiting up to 60 seconds).

Thank you! I wasn’t cleaning out the emails. This email account is used only for Google Voice, and things accumulate in it for many weeks, so I will probably need to find a script that empties it, and trigger that script at the end of the notification automation. I was tinkering with looking at the date attribute and comparing it to the incoming emails, but that looks much more laborious. As a newbie to HA, I strongly believe in keeping it simple.

Thanks again.