Yes, these emails are tied to the Stage of the Ticket.

From Helpdesk --> Configuration --> Stages, open the NEW stage and you can access the default Helpdesk: Ticket Received email template. This is where you can edit the wording.

You can also edit the global QWeb View that defines the design of all outgoing emails from Odoo. This is where you can make the style changes.

For example, in Developer Mode, you can access Settings --> Technical --> User Interface --> Views and locate the mail_notification_light View.

Create your own View that inherts this one and make the next step of changes there.  

Example:

Code:

<data>
    
<xpath expr="//table[@role='presentation']" position="attributes">
    <attribute name="style">padding-top: 16px; background-color: #ffffff; font-family:Verdana, Arial,
    sans-serif; color: #454748; width: 100%; border-collapse:separate;</attribute>
</xpath>

<td position="attributes">
    <attribute name="align">left</attribute>
</td>

<xpath expr="//t/html/body/table/tr[2]" position="replace">
<!-- POWERED BY -->
<tr><td align="center" style="min-width: 590px;">
    <!--
        Powered by <a target="_blank" href="https://www.odoo.com?utm_source=db&amp;utm_medium=email" 
               t-att-style="'color: ' + (company.email_secondary_color or '#875A7B') + ';'">Odoo</a>
    -->
    <span t-if="show_unfollow" id="mail_unfollow">
        | <a href="/mail/unfollow" style="text-decoration:none; color:#555555;">Unfollow</a>
    </span>
</td></tr>
</xpath>

</data>

Result:

See our documentation at:

https://www.odoo.com/documentation/18.0/applications/services/helpdesk/overview/stages.html

https://www.odoo.com/documentation/18.0/applications/general/companies/email_template.html

https://www.odoo.com/documentation/18.0/developer/reference/frontend/qweb.html

Your Odoo Digital Advisor or Odoo Partner can help if you don't have the technical skills to do this.