Film festivals will list acceptable submission formats in their applications, whether they use online services like WAB or paper forms, etc. In our case, we only accept submissions in Region 1 or 0 DVD, and NTSC VHS. We are well aware that filmmakers today are using all kinds of impressive, state-of-the-art, fancy-schmancy digital formats, and that some of them are living in other countries where NTSC is not the standard.
However, our reasons for limiting submissions is not arbitrary. As the project of a non-profit organization, everyone, from the co-directors to the screening committee to the ticket sellers, is a volunteer. The only way we can screen your entry is to watch it in our homes. And until your film school's digital lab's technology becomes standard in the average home in North Mississippi, we beg of you, the submitting filmmaker, to please just follow directions, and send us what we have asked for. If we are impressed with your work, and invite you to join us in February, we will ask for a festival copy, and then you can send us a mini-DV, etc. (But no BetaSP, nor 35mm, until Santa Claus donates that equipment to us before the next festival.)
In the past, we have emailed filmmakers to request a compatible copy of their entries to replace the incompatible entries, but as we receive more and more entries, we may not be able to extend this courtesy much longer. At any rate, it's bad etiquette. Would you send a format to Sundance that they didn't ask for? Probably not, as it would be a waste of their time and your money. And while we are not Sundance (though we dare to dream), we don't enjoy wasting our time either.
So, in conclusion: keep those entries coming, but please (PLEASE) follow directions.