我明白你的问题啦——你现在直接把HTML文件路径赋值给 .HTMLBody ，Outlook当然只会把它当纯文本显示，而不会去读取文件里的HTML内容。咱们得先把本地HTML文件的代码读成字符串，再放到邮件的HTMLBody里，还要结合你原来的签名逻辑，我给你一步步改代码：

第一步：先写一个读取HTML文件的工具函数 #

咱们用 Scripting.FileSystemObject 来读取本地HTML文件的全部内容，这个方法兼容性好，不用额外引用库：

Function ReadHTMLFile(filePath As String) As String
    Dim fso As Object
    Dim textStream As Object
    Dim fullHTML As String
    ' 初始化文件系统对象
    Set fso = CreateObject("Scripting.FileSystemObject")
    ' 打开HTML文件（1代表只读模式）
    Set textStream = fso.OpenTextFile(filePath, 1)
    ' 读取文件全部内容
    fullHTML = textStream.ReadAll
    ' 关闭文件
    textStream.Close
    ' 返回读取到的HTML内容
    ReadHTMLFile = fullHTML
End Function

第二步：修改你的主代码（解决核心问题+修复小bug） #

我帮你统一了变量名、补全了Late Binding下的Outlook常量（因为你用 CreateObject 而不是引用Outlook库，VBA不知道 olFormatHTML 这些内置常量），关键是替换了直接赋值路径的错误逻辑：

' 先定义Outlook常量（Late Binding下必须手动定义，不然会报错）
Const olMinimized As Integer = 1
Const olFormatHTML As Integer = 2
Const olMailItem As Integer = 0
Sub SendJobReceivedEmail()
    Dim WatchRange As Range
    Dim r As Double
    Dim Low As Long, High As Long
    Dim OutApp As Object
    Dim OutMail As Object
    Dim signature As String
    Dim htmlFilePath As String
    ' 定义要监控的单元格范围
    Set WatchRange = ThisWorkbook.ActiveSheet.Range("I3:I100")
    ' 检查是否在监控范围内触发了修改，且值为"Pending"
    If Not Intersect(Target, WatchRange) Is Nothing Then
        If Intersect(Target, WatchRange).Value = "Pending" Then
            ' 生成随机AES编号
            Low = 1
            High = 999999
            r = Int((High - Low + 1) * Rnd() + Low)
            ThisWorkbook.ActiveSheet.Cells(ActiveCell.Row, "C").Value = "AES" & r
            ' 初始化Outlook对象
            Set OutApp = CreateObject("Outlook.Application")
            With OutApp
                .ActiveWindow.WindowState = olMinimized ' 最小化Outlook窗口
                .Session.Logon ' 登录Outlook会话
            End With
            ' 创建新邮件
            Set OutMail = OutApp.CreateItem(olMailItem)
            ' 先显示邮件获取默认签名
            On Error Resume Next
            With OutMail
                .BodyFormat = olFormatHTML
                .Display ' 必须先Display才能获取签名
            End With
            On Error GoTo 0 ' 恢复错误捕获
            signature = OutMail.HTMLBody ' 保存默认HTML签名
            ' 开始配置邮件内容
            With OutMail
                .To = ThisWorkbook.ActiveSheet.Cells(ActiveCell.Row, "G").Value
                .CC = ""
                .BCC = "salesteam@allemergencyservices.com"
                .Subject = "Your Quote - ID: " & ThisWorkbook.ActiveSheet.Cells(ActiveCell.Row, "C").Value
                .BodyFormat = olFormatHTML
                ' 读取本地HTML文件内容，拼接签名
                htmlFilePath = "C:\Users\sales1\OneDrive - All Emergency Services Company\Documents\Mark O'Brien - Accounts Onboarding Tracker\ChkT - Email Template\Review\index.html"
                If Time < TimeValue("12:00:00") Then
                    .HTMLBody = ReadHTMLFile(htmlFilePath) & signature
                End If
                ' 测试阶段可以把.Send改成.Display，先预览邮件再发送
                ' .Display
                .Send
                .ReadReceiptRequested = False
            End With
            ' 释放Outlook对象（避免内存泄漏）
            Set OutMail = Nothing
            Set OutApp = Nothing
        End If