Comment # 5 on bug 76273 from Patrick Ohly

503 sounds like activesyncd is really talking to the ActiveSync server and
getting that error back. Perhaps logs of activesyncd or the ActiveSync server
explain that?

For local logging, set EAS_DEBUG and (to avoid flooding the console)
EAS_DEBUG_FILE before running activesyncd.

For example:
dbus-session.sh bash
EAS_DEBUG_FILE=activesyncd.log EAS_DEBUG=5 <path>/activesyncd
syncevolution --print-databases ...