Welcome to the forum! There are a lot of great people here willing to lend a hand anytime. Often using the search feature (in the toolbar at the top of every page) will lead you to the answers you're looking for. If not, feel free to post a question in the appropriate area.
Please take a moment to view the information linked below my signature to get the most out of your iPad as well as our forum.
With respect to your question, that's an issue that's been around for years. It generally happens to Exchange and GMail accounts for some reason. No one really knows why. You can Google it for more info.
There are a number of "fixes" including just restarting your mail program on your iPad or restarting your iPad itself. More here:
iPhone, iPad, iPod touch: Turning off and on (restarting) and resetting
Others have gone to the source, their mail account on a computer, and removed them. Apparently it's nothing to worry about, just a nuisance.
Let us know if that helps. Others may have some more suggestions as well.
BTW, I moved your post to the iPad Help area where you're likely to get a better response to your question.
Welcome again and enjoy!
