在用ASP编写页面时，如果涉及到邮件发送，一般会要求输入Email地址。错误的Email地址往往带来许多不必要的麻烦，用下面的函数IsValidEmail就能判断出一个Email地址是否有效。

函数源代码：
<%
Function IsValidEmail(Email)
ValidFlag = False
If (Email <> "") And (InStr(1, Email, "@") > 0) And (InStr(1, Email, ".") > 0) Then
atCount = 0
SpecialFlag = False
For atLoop = 1 To Len(Email)
atChr = Mid(Email, atLoop, 1)
If atChr = "@" Then atCount = atCount + 1
If (atChr >= Chr(32)) And (atChr <= Chr(44)) Then SpecialFlag = True
If (atChr = Chr(47)) Or (atChr = Chr(96)) Or (atChr >= Chr(123)) Then SpecialFlag = True
If (atChr >= Chr(58)) And (atChr <= Chr(63)) Then SpecialFlag = True
If (atChr >= Chr(91)) And (atChr <= Chr(94)) Then SpecialFlag = True
Next
If (atCount = 1) And (SpecialFlag = False) Then
BadFlag = False
tAry1 = Split(Email, "@")
UserName = tAry1(0)
DomainName = tAry1(1)
If (UserName = "") Or (DomainName = "") Then BadFlag = True
If Mid(DomainName, 1, 1) = "." then BadFlag = True
If Mid(DomainName, Len(DomainName), 1) = "." then BadFlag = True
ValidFlag = True
End If
End If
If BadFlag = True Then ValidFlag = False
IsValidEmail = ValidFlag
End Function
%>

用法举例：
IsValidEmail("my_263_email@263.net") 返回Ture
IsValidEmail("zh99wj@tonghua.com.cn") 返回Ture
IsValidEmail("myemail263.net") 返回False
IsValidEmail("my_263_email@263) 返回False
请注意，函数只是判断Email地址格式是否有效，但并不能检查该地址是否确实存在。