I had two similar things happen, I used to release the quarantined emails on our IronPort's.
One morning an email was stuck for our State Sales Manager, we used to check why the message was quarantined as usually it was just the profanity filter, boy did I get a surprise when the embedded image of his wife came up, for a woman in her late 40's she was seriously hot.
I spoke to him quietly about it and mentioned it was best not to send personal emails using his work email, I could do this because I had a very good rapport with HR, CEO, CIO and CFO and they knew I don't muck around.
The next one was a few months later when one of the junior sales ladies sent an email to the same Manager detailing what they did the night before.
That one got deleted, however I sent a company wide email to all staff advising them as per policy, that whilst we did allow some personal use, we had been receiving emails lately that were not acceptable and as we do check quarantined emails to find out why they get stuck and as people tend to blurt everything out in the first lines of the email, that we really didn't need to know some of the things that we had found lately.
Suffice to say, I had no problems after that.