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.
Mae un o'ch hidlau'n cynnwys pennyn cyfaddasu sy'n cynnwys nod annilys, fel ':', nod anargraffadwy, nod nad yw'n ascii neu nod ascii wyth did. Golygwch y ffeil msgFilterRulesrules.dat, sy'n cynnwys eich hidlau, i dynnu'r nodau annilys o'ch pennyn cyfaddasu.