I have discovered that when people reply to emails sent from Servicedesk, that the mail fetcher drops the mail, with the following system log message: "Mail Filter condition matched. Hence not adding the email as conversation."

I cannot see anywhere in Servicedesk, where this option is set.

The mail spam filter is only set to drop mails not containing '##', and when this condition is met the system log writes "Mail Filter condition matched. Hence not creating a new request." which is ok.

Under 'General Settings' the option "Process emails received from new email addresses ?" is set to 'Yes'

Does anyone have a solution to this problem?