I don't think you want an input mask for email? I believe you want to check for a valid email address and to do that you need to check for the @ symbol and once you got that then check for a . .
so something like this would work on the before update event of the email object.
Dim strCheckEmail As String
Dim strCheckPosition As String
Dim varChkEmail As Variant
varChkEmail = Me("txtEmailAddr"

strCheckEmail = IIf(IsNull(varChkEmail), "", varChkEmail)
'*Apply the conditions
If Trim(strCheckEmail) <> "" Then
'* Check to see if we have an @ symbol
strCheckPosition = InStr(1, strCheckEmail, "@"
'* strCheckPosition returns true if we got an @ symbol
'* if strCheckPosition returns False then display an error
'* message and wait for the correct email.
If strCheckPosition = 0 Then
MsgBox "Invalid E-Mail please check your entry" & vbCrLf _
& "before continuing.", vbCritical, "Error E-Mail"
Cancel = True
GoTo SubExit
ElseIf strCheckPosition > 0 Then
'*we got an @ symbol now check for a dot
If InStr(strCheckPosition, strCheckEmail, "."

> 0 Then
Me("cmdEMail"

.Enabled = Not (IsNull(varChkEmail))
Else
MsgBox "Invalid E-Mail please repair or remove" & vbCrLf _
& "your entry before continuing.", vbCritical, "Error E-Mail"
Cancel = True
End If
End If
End If Life's a journey enjoy the ride...
jazzz