A paper I have been working on for well over a year is finally reaching submission stage. At the beginning of the project, I have received detailed explanations from two professors about the mathematical derivation of an algorithm that they designed, and that I applied to my problem. Their help is acknowledged in the appropriate section of the paper, and the paper presenting the algorithm is cited in the bibliography. We never met in person and only interacted by e-mail as a result of my questions.
I am considering sending a new e-mail to thank them again and let them know about the acknowledgement. On the one hand, I am afraid they might think I am spamming to draw attention to my research. On the other hand, our field of research are distant enough that they may never read the acknowledgement, making it a little pointless.
Is it common to notify people you acknowledge in a research paper in this way?