Time Travel, Grammar and The Postal Service
First of all, many thanks to Vrinda for giving the idea for this...babble.
The world today is connected. Exceedingly well. In Victorian times, or a little closer to home, messages would take weeks to get across, with the advent of faster telecommunications, days, and soon enough you could send a telegram, but only if you were packing a lot of wads in yer wallet. Basically, the cheapest, if not fastest, method of communication for a very long time was Postal Mail, hereby reffered to as "snail mail", not in any ways to be confused with the far more elaborate "Snail Mail".
After the internet revolution, the world changed. Whever the hell you were, it had suddenly become affordable (but only just) to send messages across instataneously. There was email, there was ISD that didn't involve booking calls on a trunk line, there was basically a whole lot of change. As we entered a new century, we got VOIP, net conferencing, Mobile Phones, and finally SMS. Prices plummeted, and suddenly, everyone could get the message, quite literally.
Charms of the old fashioned system, as it is with most old fashioned systems, fail to be lost. Thus, the postal system in most countries has not, in fact, become obsolete. They're enough people sending mail here and there to keep it going. In fact, Japan even plans to privatise it, if their Richard Gere-esque Prime Minister can manage to get himself re-elected. The problem is, most information you wish to convey by snail mail has, in all probability, already happened, and with even greater probability already been discussed amongst the parties involved in the whole mailing experience.
Douglas Adams, whom I'm sure you're all familiar with, covered the nasty world of punctuation over time gaps quite well in his book, The Restraunt At the End of the Universe. I offer here the link that covers his views, in the form of Dr. Streetmentioner's Time Travel Handbook Of 1001 Tense Formations. The fact is, that you need these to describe events in a snail mail that will happen in your future, but have already happened by the time the reader has read the mail, and he or she is already aware of the said event's occurance. Tense and Grammar, as certain Violent Panda's and Annoying Short Guy's have pointed out time and time again, are very important.
Seeing how this is the only real way you're going to attempt time travel, you might as well give it a shot. For now, I wioll haven be have cake.