“…it is 100% necessary to send an email…”
I take it a step further. I always send a hand written Thank You Note by snail mail. Always. I have never failed to do this.
Why? Because if someone has spent an hour of their time (I don’t care if it’s on company time) to potentially change my life, the least I could do is take 5 minutes to share a sincere Thank You. I always take the time to hand write it, I always make it personal, and I am always sincere. (If you’re going to be even 1% phony, don’t bother, people will see right through it).
There are some nice byproducts. It demonstrates professional courtesy. It demonstrates good communication skills. It demonstrates good customer service. It gets you remembered. Every time.
But I don’t do it for these reasons. I do it because it’s the right thing to do. It is never “annoying” or a “detriment”. Almost everyone I have ever sent a hand written note has told me that they really appreciated opening it and reading it.
Sometimes I even take it a step further. Several times, I have asked public speakers what their favorite restaurant is, and then sent a gift card in the Thank You note. I really want them to understand what a difference their contribution has made in at least one attendee’s life. The gift card is a nice idea because I know they will use it and enjoy it, and maybe even think of me that night. I would never send a gift to an interviewer - that’s not the same thing.