Error fetching email via pop3s with attachments

I just noticed this error after fetching emails with Outlook.

mail 0017 POP3S !ERROR opening/encoding/sending /sbbs/data/file/0001.in/Z1BINKD.TXT

The only thing in my mail log is

Apr 8 02:31:38 bbs synchronet: mail 0017 POP3S MIME Encoding and sending /sbbs/data/file/0001.in/Z1BINKD.TXT Apr 8 02:31:38 bbs synchronet: mail 0017 POP3S !ERROR opening/encoding/sending /sbbs/data/file/0001.in/Z1BINKD.TXT