How to check for a valid EMail Address format in Delphi

Now a days most of applications have facility to send Email to Users with some information. So before send Email we generally check for valid Email address format. Here I have 2 approaches how to validate an Email address format in Delphi.

1. Validating Email addresses format using Regular Expression
A regular expression is a special text that we can use as a search pattern. So for this we can use a regular expression string to check Email address syntax. And Delphi XE or later versions provide TRegEx class to use regular expression functions. So we can use this approach only on Delphi XE or latter versions. But for this we have to use System.RegularExpressions unit in Uses part. 
....

    function IsMatch(const Input, Pattern: string): boolean;
    function IsValidEmailRegEx(const EmailAddress: string): boolean;
....
function TForm1.IsMatch(const Input, Pattern: string): boolean;
begin
  Result := TRegEx.IsMatch(Input, Pattern);
end;
function TForm1.IsValidEmailRegEx(const EmailAddress: string): boolean;
const
  EMAIL_REGEX = '^((?>[a-zA-Z\d!#$%&''*+\-/=?^_`{|}~]+\x20*|"((?=[\x01-\x7f])'
             +'[^"\\]|\\[\x01-\x7f])*"\x20*)*(?<angle><))?((?!\.)'
             +'(?>\.?[a-zA-Z\d!#$%&''*+\-/=?^_`{|}~]+)+|"((?=[\x01-\x7f])'
             +'[^"\\]|\\[\x01-\x7f])*")@(((?!-)[a-zA-Z\d\-]+(?<!-)\.)+[a-zA-Z]'
             +'{2,}|\[(((?(?<!\[)\.)(25[0-5]|2[0-4]\d|[01]?\d?\d))'
             +'{4}|[a-zA-Z\d\-]*[a-zA-Z\d]:((?=[\x01-\x7f])[^\\\[\]]|\\'
             +'[\x01-\x7f])+)\])(?(angle)>)$';
begin
  Result := IsMatch(EmailAddress, EMAIL_REGEX);
end;
....
Use of above functions....
procedure TForm1.btnValidateEmailregxClick(Sender: TObject);
begin
  if IsValidEmailRegEx(EditEmail.Text) then
    ShowMessage('Valid Email Address')
  else
    ShowMessage('InValid Email Address');
end;

2. To check Email address format manually with a user defined function in Delphi
In this part I have created a function in Delphi to check all characters of the Email address that the character is a valid character for Email or not.
.....
    function IsValidEmail(const Value: string): boolean;
.....
function TForm1.IsValidEmail(const Value: string): boolean;
  function CheckAllowed(const s: string): boolean;
  var
    i: integer;
  begin
    Result:= False;
    for i:= 1 to Length(s) do
    begin
      // illegal char - no valid address
      if not (s[i] in ['a'..'z','A'..'Z','0'..'9','_','-','.','+']) then
        Exit;
    end;
    Result:= True;
  end;
var
  i: integer;
  namePart, serverPart: string;
begin
  Result:= False;

  i:= Pos('@', Value);
  if (i = 0) then
    Exit;

  if(pos('..', Value) > 0) or (pos('@@', Value) > 0) or (pos('.@', Value) > 0)then
    Exit;

  if(pos('.', Value) = 1) or (pos('@', Value) = 1) then
    Exit;

  namePart:= Copy(Value, 1, i - 1);
  serverPart:= Copy(Value, i + 1, Length(Value));
  if (Length(namePart) = 0)  or (Length(serverPart) < 5)    then
    Exit;                      // too short

  i:= Pos('.', serverPart);
  // must have dot and at least 3 places from end
  if (i=0) or (i>(Length(serverPart)-2)) then
    Exit;

  Result:= CheckAllowed(namePart) and CheckAllowed(serverPart);
end;
.....
procedure TForm1.btnValidateEmailClick(Sender: TObject);
begin
  if IsValidEmail(EditEmail.Text) then
    ShowMessage('Valid Email Address')
  else
    ShowMessage('InValid Email Address');
end;

Please note that 1st approach will not work on Delphi versions before Delphi XE because handling of regular expression functions are introduced from Delphi XE. So for Delphi 2010, 2006, 7, 6 or lower versions use 2nd approach to validate a Email address.

Comments

  1. It is really good function. Thanks for this.
    I think we do need little bit improve of this function (IsValidEmail).

    if (pos('..', Value) > 0) or
    (pos('@@', Value) > 0) or
    (pos('.@', Value) > 0) or
    (pos('@.', Value) > 0) then
    Exit;

    if(Value[Length(Value)] = '.') or (Value[Length(Value)] = '@') then
    Exit;

    ReplyDelete
  2. How can I upgrade my Delphi software

    ReplyDelete
  3. Thanks for sharing this well written email checker online in Delphi

    ReplyDelete
  4. Sorry. Can't say "thanks". MN@abcLOL.com is not working ;-)

    ReplyDelete

  5. I think the admin of this website is really working hard for his site, because here every information is quality based information.
    Email Validation Api- Antideo

    ReplyDelete
  6. It’s hard to search out educated folks on this topic, but you sound like you know what you’re speaking about! Thanks
    Free Email Validator

    ReplyDelete
  7. Thanks for your write-up. What I want to point out is that while searching for a good on-line electronics go shopping, look for a internet site with complete information on critical indicators such as the level of privacy statement, safety details, payment guidelines, along with terms as well as policies. Always take time to read the help and also FAQ areas to get a greater idea of how the shop operates, what they can do for you, and how you can use the features.
    Email Address Checker

    ReplyDelete
  8. In addition to restrictions on syntax, there is a length limit on email addresses. That limit is a maximum of 64 characters (octets) in the "local part" (before the "@") and a maximum of 255 characters (octets) in the domain part (after the "@") for a total length of 320 characters.

    ReplyDelete
  9. You should study RFC3696 before claiming to provide ways to check for valid email addresses.

    if not (s[i] in ['a'..'z','A'..'Z','0'..'9','_','-','.','+']) then Exit;

    is simply incorrect.


    ReplyDelete
  10. Is an email a Char or String

    ReplyDelete
  11. According to wikipedia https://en.wikipedia.org/wiki/Email_address local domain name with no TLD e.g. admin@mailserver1 is valid email address, however your function says it is not.

    ReplyDelete
  12. if the email starts with dash "-" this function is not working.

    ReplyDelete

Post a Comment

Popular posts from this blog

ShellExecute in Delphi

How to send Email in Delphi?

Drawing Shapes in Delphi