One of your filters uses a custom header that contains an invalid character, such as ':', a non-printable character, a non-ascii character, or an eight-bit ascii character. Please edit the msgFilterRules.dat file, which contains your filters, to remove invalid characters from your custom headers.
Tha caractair mì-dhligheach ann an criathrag agad, leithid ':', caractair nach gabh a chlò-bhualadh, caractair nach eil air nòs ascii no caractair eight bit ascii. Deasaich am faidhle msgFilterRules.dat (far a bheil na criathragan agad) 's tu a' toirt air falbh na caractairean mì-dhligheach o na bannan-cinn gnàthaichte agad.