Dear Agent Manners:
When corresponding with an agent one has queried, it is incorrect (or annoying; is there a difference?) to reply a “thanks for the info!” to reply from said agent. A for-instance would be, did you in fact get my partial you requested, to which the agent says, sure did, just behind, and would be author writes back, thanks. Or is it better to keep the inbox less cluttered and feel rude by failing to thank them for responding?
That sounded cluttered right there. Sure hope my novel is better.
Agent Manners’ instinct is to always suggest being considerate and polite. In this case I think you need to listen to your own instincts. If a brief thank you makes you feel that you are in a better light, by all means, something that short and requiring no reply will likely not inconvenience an agent. That said, agents do get quite a lot in the inbox, so if your sense that it would be an imposition is stronger, simply wait for their reply on the materials.