Not answering is an answer. People read it, so own what you’re saying with it.

Silence gets read, always. The other person fills it in, usually with the least generous version, and the longer it runs the more certain that version becomes. Sometimes not replying is exactly what you mean, and that is a legitimate message. The trouble is when you intend nothing by it and the other person receives a verdict.

Look at who you have left waiting and decide what you are actually saying to each of them. Where the answer is no, send it in a line. Where you have not got round to it, say that, since people can hold a delay once they know it is one.