Initialisms can be great (and, yes, I mean ‘Initialism’ rather than ‘abbreviation’, as it’s the correct term in this case). However, when they’re simply not required and it may not be a universal term then you should always be careful of their use. I mention this when I had an email today stating…

I am OOTO today

I didn’t catch on at first but soon realised they meant ‘out of the office’. I’d come across OOO and OOF before (the latter is a Microsoft thing – “out of facility”) but not this one. Except, this is an email responder and not Twitter – no shortening was required. How much clearer would it have been to have simply said “I am out of the office today”. They’re rarely this short overall anyway, with messages often looking more like this…

I am OOO until Wednesday. In my absence, please contact Bob for any urgent queries.

Now, seriously, what is the point of shortening “out of office” here? At Automattic we use AFK (“away from keyboard”) but I wouldn’t think of using this externally.

Be professional and be clear – anyone receiving your reply shouldn’t be puzzled (even if just at first) by what you mean.