Since switching temporarily to using the webmail interface on Build 7719 (Feb 18, 2021) I've noticed that sometimes, perhaps one in ten emails, clicking the Send button does nothing. I can see the little animated fade onclick, but the button remains blue. Sometimes I get a red alert in the bottom right corner telling me it failed to save a draft, and each click of the send button pops up another alert. The only remedy at that point is to copy the content of my email to the clipboard, close that window, and reply again, pasting my content in, and then clicking send.

I haven't been able to forcibly replicate the behavior, but it happens often enough that I'm thinking it must also be happening for my customers.

I don't want to open a ticket about this because I can't replicate it, and I'm not sure if anyone else is seeing this behavior.