I am on Apple Mail 10.3 with Sierra OS. Suggesting to type in gibberish in the pasword area and wait, then re-type known password does not work for me.
Since I reinstalled Sierra OS on my Mac, I worked with an Apple Sr. Tech to reconfig my email accounts and he could not resolve this issue. He told me to contact Comcast Tech Support. After no resolution with Comcast, they passed the buck back to Apple. Comcast servers not recognizing my password for outgoing mail. Also changes password before my eyes when I type in manually and wait a few seconds, per your instruction on this forum. My password is recognized from the Comcast website though.
I followed the online documentation. Comcast tech directed me to the Comcast CSA Dept. tomorrow morning. Bad solution. Sr. tech support should be available up until 9 pm.
Really Comcast. You should get together with Apple to troubleshoot this bug since Apple products are used by so many people.
... View more