It's obvious that a vote to leave the EU is a vote to shake things up and create uncertainty in the short-term. On the other side of that period? Who knows?
Businesses, anyway, are understandably wary of uncertainty where possible, and in that sense I don't think it's unreasonable to send an email along the lines of "if the UK votes to leave the EU then we can't predict what will happen, so stay tuned and be aware that this may well affect your jobs somehow."
Anything too strong would risk politicising an internal business email a little too much -- but on the other hand Brexitters really need to stop crying scaremonger any time someone suggests that there may be negative consequences of leaving the EU. Of *course* it's going to be messy; of *course* the outcome depends on how the EU decides to react to a "no" vote; of *course* no-one can say exactly what will happen, which includes all the BS Brexit seems to want to sell about a ticket to paradise.