Email Template in odoo

1. Make one email template file inside data folder inside addons of your application and mention on manifest file as well.

  example: student_email.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data noupdate="1">
        <record id="school_student_invitation_mail_template" model="mail.template">
            <field name="name">Invitation Mail</field>
            <field name="model_id" ref="school.model_school_student"/>
            <field name="subject">Invitation Mail</field>
            <field name="email_to">{{object.email}}</field>

            <!-- for attachment  -->
            <field name="report_template" ref="module_name.action_id_of_report"/>
            <field name="report_name">Student_{{object.name}}_report</field>
            <field name="body_html" type="html">

            <!-- custom variable  -->
                <t t-set='user' t-value='object'/>
                <span t-out='user.name'/>
                <span t-out='user.get_full_name()'/>
            <!-- custom variable  -->
                <t t-set='count' t-value='0'/>
                <t t-set='count' t-value='count+1'/>
               


                <p>Hello, <span t-field="object.name"/>.</p>
                <p>Welcome to <t t-out="env.company.name or ''">YourCompany</t>! We are thrilled to have you on our family.</p>
                <p>Email: <span t-out="object.email"/></p>

                <!-- condition rendering  -->
                <p t-if='object.phone'>Phone: <span t-out="object.phone"/></p>

                <t t-if='object.department_id'>
                <p>Department: <span t-field='object.department_id.name'/></p>        
                </t>
                <t t-elif='object.semester_id'>
                <p>Semester: <span t-field='object.semester_id.name'/></p>        
                </t>
                <t t-else=''>
                <p>Age: <span t-field='object.age'/></p>        
                </t>
                 

                 <!-- looping  -->
                <t t-if='object.id in [1,2,3,4,5,6,7,8,9]'>
                <p>User found</p>
                </t>

                <p>Language List</p>
                <t t-set="languages" t-value="['english','nepali','hindi']"/>
                <t t-foreach='languages' t-as='language'>
                <ul>(<span t-out='language_index'/>) <span t-out='language'/></ul>
                <ul> <span t-out='language_odd'/></ul>
                <ul> <span t-out='language_even'/></ul>
                <ul> <span t-out='language_first'/></ul>
                <ul> <span t-out='language_last'/></ul>
                <ul> <span t-out='language_rct'/></ul>
                <ul> <span t-out='language_rct_value'/></ul>
                <ul> <span t-out='language_parity'/></ul>
                </t>

                <!-- image  -->
                <image src='/school/static/description/icon.png' style='width:50px;height:50px,object-fit:cover;' alt='image-not-found'/>
                <br/>
                <image t-attf-src='data:image/png;base64,{{object.image}}' style='width:50px;height:50px,object-fit:cover;' alt='image-not-found'/>
                
                <p>Email: <span t-out="object.email"/></p>
                <br/>
                <p>If you have any questions or need assistance, feel free to reach out to our support team.</p>
                <p>Best regards,</p>
                <p><t t-out="env.company.name or ''">YourCompany</t></p>
        </field>

        </record>
    </data>
</odoo>

2.How to sent email from code

def sending_mail(self):
    self.env.ref('module_name.email_template_record_id').send_mail(self.id,force_send=True)

how to send email by button click

def send_mail(self):
    template_id=self.env['model_name.template_id'].id
    templte=self.env['mail.template'].browse(template_id)
    template.send_mail(self.id,force_send=True)
    # here self.id is the record id of btn click