by Ian Lent (6 Submissions)
Category: String Manipulation
Compatability: Visual Basic 4.0 (32-bit)
Difficulty: Unknown Difficulty
Originally Published: Tue 24th August 1999
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
Comprehensive e-mail address syntax validation check
VBcoders
' Purpose: Validate a given e-mail address.
' In: strAddress - string to be validated
' Out:
' Returns: True if strAddress is a valid e-mail address; False otherwise.
' Date: 8/23/1999
' Programmer: Ian Lent and Melvin Tucker
' Last Modified:
Dim lngIndex As Long ' Position in strAddress
Dim lngCountAt As Long ' Number of "@"
Dim lngLastDotPos As Long ' Position of the previous dot in the string
Dim strCurrentChar As String ' Buffer that holds the contents of the string one char at a time.
On Error GoTo Fail_Validation
ValidateEMail = True ' Prove me wrong!
strAddress = Trim(strAddress)
lngLastDotPos = 0
lngCountAt = 0
' If the address isn't at least this ([email protected]) long,
' it's not a valid address.
If Len(strAddress) < 7 Then GoTo Fail_Validation
' Check for certain generably allowable characters in the leading position.
' If found, it's not a valid address.
strCurrentChar = Left$(strAddress, 1)
If strCurrentChar = "." Or strCurrentChar = "@" Or strCurrentChar = "_" Or _
strCurrentChar = "-" Then GoTo Fail_Validation
' Check the string for non-allowable characters.
For lngIndex = 1 To Len(strAddress)
strCurrentChar = Mid$(strAddress, lngIndex, 1)
' Count the number of "@".
If strCurrentChar = "@" Then lngCountAt = lngCountAt + 1
' If there are two consecutive dots, it's not a valid address.
If strCurrentChar = "." Then
If lngIndex = lngLastDotPos + 1 Then
GoTo Fail_Validation
Else
lngLastDotPos = lngIndex
End If
End If
Select Case Asc(strCurrentChar)
' These characters are not allowable in e-mail addresses.
Case 1 To 44, 47, 58 To 63, 91 To 94, 96, 123 To 127, 128 To 255
GoTo Fail_Validation
End Select
Next lngIndex
' If there isn't one, and only one "@", then it's not a valid address.
If lngCountAt <> 1 Then GoTo Fail_Validation
' If the extension isn't a known one, it's not a valid address.
Select Case Right$(strAddress, 4)
Case ".com", ".org", ".net", ".edu", ".mil", ".gov"
' Yes, it's valid.
Case Else
GoTo Fail_Validation
End Select
ValidateEMail_Exit:
Exit Function
Fail_Validation:
ValidateEMail = False
GoTo ValidateEMail_Exit
End Function
