This same situation happened a little over a year ago and I did notice Zimbra truncated my password by 2 characters. Anyway, filing a bug report did result in a fairly rapid fix. If Zimbra is truly EOL then what other similar product is avail. My old Outlook stopped working about 3 years ago after one of the wonderful Win 7 "updates" (actually deliberate code addition to slow down your PC) and Zimbra has carried the water since then.
I tried Evolution but that was 100% useless and I was never able to receive a single e-mail from Yahoo.
So again what are the options.