What is the major difference between these two sentences? Are they interchangeable? And why do we use the 2nd one at all, what is the necessary? <br/><br/>1. Email me if you have any questions<br/>2. Email me should you have any questions. <br/><br/>Thanks <img class='emoticon' style='Width:19px;Height:19px;' data-delaysrc='https://uat-englishforward-forums-backend.s3.us-west-2.amazonaws.com/Emoticons/1.gif' src='https://uat-englishforward-forums-backend.s3.us-west-2.amazonaws.com/Emoticons/1.gif' alt='Emotion: smile'/>