Ghost/ghost/admin/app/templates/components/gh-post-settings-menu/email.hbs

<div class="settings-menu-header subview">
    <button {{on "click" this.close}} class="back settings-menu-header-action" data-test-button="close-psm-subview">{{svg-jar "arrow-left"}}<span class="hidden">Back</span></button>
    <h4>Email newsletter</h4>
    <div style="width:23px;"></div>
</div>

<div class="settings-menu-content settings-menu-email">
    {{#if post.email}}
        {{!-- Mail has already been sent --}}
        <p>Subject: {{this.post.email.subject}}</p>
        <p>Status: {{this.post.email.status}}</p>
        <p>Sent on: {{gh-format-post-time this.post.email.createdAtUTC}}</p>
        <p>Sent to {{pluralize this.post.email.emailCount "member"}}</p>
        <p><button {{on "click" this.toggleEmailPreview}}>View email</button></p>
    {{else}}
        {{!-- Mail not sent yet --}}
        {{#if mailgunError}}
            <p class="gh-box gh-box-warning settings-menu-mailgun-warning">
                {{svg-jar "info" class="w5 h5 fill-yellow nl1"}}
                You need to configure Mailgun in {{#link-to "settings.labs" data-test-nav="labs"}}Labs → Members settings{{/link-to}} to enable email newsletters.
            </p>
        {{/if}}

        <form {{action "discardEnter" on="submit"}}>
            {{#gh-form-group errors=post.errors hasValidated=post.hasValidated property="emailSubject"}}
                <label for="og-title">Subject</label>
                {{gh-text-input
                    class="post-setting-email-subject"
                    id="email-subject"
                    name="post-setting-email-subject"
                    placeholder=(truncate emailSubject 40)
                    value=(readonly emailSubjectScratch)
                    input=(action (mut emailSubjectScratch) value="target.value")
                    focus-out=(action "setEmailSubject" emailSubjectScratch)
                    stopEnterKeyDownPropagation=true
                    disabled=mailgunError
                    data-test-field="email-subject"}}
                {{gh-error-message errors=post.errors property="emailSubject" data-test-error="email-subject"}}
            {{/gh-form-group}}

            <div class="form-group">
                <div class="flex">
                    <label class="nowrap flex-auto">Test email</label>
                    <button type="button" class="gh-btn gh-btn-link settings-menu-email-button" {{on "click" this.toggleEmailPreview}} data-test-button="toggle-email-preview">
                        <span class="blue">
                            Preview in browser
                        </span>
                    </button>
                </div>

                <div class="{{if mailgunError "disabled"}}">
                    {{gh-text-input
                        class="post-setting-email-test"
                        id="email-test"
                        name="post-setting-email-test"
                        placeholder="noreply@example.com"
                        value=testEmailAddress
                        stopEnterKeyDownPropagation=true
                        disabled=mailgunError
                        data-test-field="email-test"}}

                    {{#if sendTestEmailError}}
                        <div class="error"><p class="response">{{sendTestEmailError}}</p></div>
                    {{/if}}

                    {{gh-task-button "Send test email"
                        task=sendTestEmail
                        successText="Email sent"
                        runningText="Sending..."
                        class="gh-btn w-100 mt2 gh-btn-icon"
                        disabled=mailgunError
                        data-test-send-test-mail=true
                    }}
                </div>
            </div>
        </form>
    {{/if}}
</div>