Not "well-received", but just "Received, with thanks." or just "Thank you!". The fact that you responded to an email with "Thank you" implies that you received it (otherwise how could you reply?) and also sends thanks, so that's enough. :) "Well-received" is an expression that generally means that something was liked or appreciated. "Her performance in the play was well-received". The hyphen makes the expression easier to read and easier to tell apart from constructs such as "the well received the coin I threw into it". Unfortunately it's more common than not for people to leave the hyphen out, and there are a million such cases that could be just a tiny bit more comfortable to read, and to understand without re-reading, if folks used hyphens. :)