If you're working at a large organization in a junior to mid-level role (such as a major bank), it is quite likely that you'll rarely be conversing with top-level executives or division heads .
Despite that your contact with them would only occur by chance or during a big presentation or meetings it doesn't hurt to put in a kind note to someone who's been instrumental in your employer's success and has decided to quit for the right reasons (ie retirement or a better role). The purpose of this is not only to improve on PR skills but to also make yourself known (even if just by face or name) in the executive's league as little gestures like these do definitely go a long way.
So how do you go about this? The sample e-mail below should explain it a bit.
Dear Mr. Smith,
Thank you for a wonderful presentation about our division's 3 month review - it always feels great being acknowledged as a team and know that even the little things we do everyday contribute to ........ (company name's) strategic success.
However this time, your kind words of encouragement coincide with your embarking upon your next journey.
Please be assured that over the past 4 years, your general presence when sitting in the vicinity of our team was always warm, welcoming and I can say it with 100% confidence that it made our entire team feel very special.
I trust the future does hold the opportunity for you to drive another business with the same amount of dedication and passion and bless it with success which you did over here.
Thank you again,
An e-mail like this is guaranteed to attract a very positive response from the outgoing executive it was addressed to and he/she will remember this gesture for a long time and it doesn't matter whether you even hardly knew this official or not.
An option is always to ask a meeting with this executive and convey some sincere words of gratitude in person but this is likely to be viewed as an overstep and might not always deliver the results you were expecting in terms of acknowledgement.
If you are considering writing something like this to congratulate a departing executive in your firm, you also need to acknowledge when would it be an proper time to do so and take into account more intangible factors such as the company culture, the person concerned and under what circumstances was he or she departing.
There's no one set formula or pattern you need to use when writing a farewell letter - at the end of the day it is best to use your own style and assess your own relationship with the person or your company to decide the best method of putting the gesture across.