[Verevkin]

Тестовое приложение:

Код:

program xxx;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils, System.RegularExpressions;

function ValidateIMAPServer(const URL: string): Boolean;
begin
  result:= TRegEx.IsMatch(URL, '(^imap\.[a-z]+\.[a-z]+$)');
end;

begin
  {$REGION 'сервера'}
  const SERVERS =
  [
    'imap.rambler.ru',
    'imap.gmail.com',
    'pop3.mail.ru',
    'imap.mail.ru',
    'pop.yandex.ru',
    'imap.yandex.ru'
  ];
  {$ENDREGION}

  try
    for var url in SERVERS do
      WriteLn(Format('%s – %s', [url, if ValidateIMAPServer(url) then 'VALID' else 'INVALID']));
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;

  readln;
end.