So, I've been puzzling for a long time over the existence of lying-like phenomena. For instance, I set up an automated website that gives false information about the weather, presenting it as true. When the website falsely says: "The current temperature in Waco is -2oC", most people will, I think, say that I haven't, strictly asserted this. After all, I might even be dead by this point. However, what I did is relevantly like lying.
Consider also a continuum of cases. I sign a letter to a third party. I know the letter contains false central claims. But there is a continum here based on how much I've contributed to the letter and how aware I am of its contents. As long as I know that the letter contains false central claims, it seems to matter little morally whether I am the sole author of the letter or have signed it without knowing any particulars about the contents—in both cases, I am dishonest in a way equivalent to lying. For purposes of the morality of honesty in communication it should not be necessary to draw the line between fully asserting and signing.
A friend suggested to me that one talk of a "constructive assertion", where "constructive" is a legal alienans adjective: a "constructive A" is not an A, but has the same normative consequences of Aing. But I think there is a simpler solution. We simply talk of the endorsement of propositions. It is wrong to endorse when one knows one is endorsing a falsehood. (That's the easy case. It may be tricky to come up with a rule that handles cases where you do not have full knowledge.)
"Endorsing propositions" generalizes "asserting propositions". For to assert a proposition is simply to present a proposition and endorse it. Actually, it may be that every full act of endorsement includes a presentation as well. After all, one's act of endorsement has to somehow indicate what proposition one is endorsing, and one has to do that by means of some linguistic or quasi-linguistic convention, such as setting down one's after a written expression of the proposition or nodding after someone else has expressed the proposition orally. If one takes this wide view of presenting a proposition, then one does in fact assert what the website says and what the letter says, even when one does not know the content of either. If one does not like this conclusion, one can give a narrow account of presenting.
A consideration in favor of the wider view is this. Suppose you assert that p, and I say: "Yes." It seems fairly reasonable to say that I've asserted that p by means of a prosentence. But there will be cases when I say it without having paid any attention to what you said, and I agree out of cowardice or trust. If one thinks that I don't assert in the website case, one should say that I don't assert in this case. But I think in this case I do assert. For take the case where I say: "Yes, p." In that case, it sure seems that I have made an assertion, even if I repeat "p" completely mechanically and absentmindedly. If so, then likewise a "Yes" without the "p" part should be an assertion. And the only reasonable thing for it to be an assertion of is that p. (One might say that "Yes" is an assertion of "I agree with what you've just said" or "What you've just said is true." But that's probably not correct, because then the "Yes" has additional entailments that the proposition that p did not have: it entails that you spoke and that I exist.)
In any case, even if one not convinced by my suggestion that all endorsement involves assertion (or re-assertion), I think it is correct to say that the general phenomenon for the morality of lying to discuss is endorsement.