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I don't know erlang, but it looks to me as it's hardcoded here https://git.kolab.org/diffusion/G/browse/master/apps/kolab_guam/src/kolab_guam_listener.erl;417fec0be3df14c157bd10915892ba8f90c224e6$78
I've updated to guam-0.8.3-1.2.fc23.kolab_wf.x86_64, still no change.
I'd really like to fix this. Do you need more logs or can I help with other diag output?
@Karl-Mendes IMAP, no? ActiveSync already filters things, of course ...