RFC2822 (https://tools.ietf.org/html/rfc2822#section-2.1.1) states that emails have a maximum line length of 998 characters.  However, SalesInbox does not adhere to this standard and sends email with line length exceeding 998 characters.  Mail Transfer Agents such as Postfix enforce the maximum line length (http://www.postfix.org/postconf.5.html#smtp_line_length_limit) by breaking lines that exceed the limit.  Since this takes place after the message has been signed by DKIM, it renders the DKIM signature invalid.  Invalid DKIM signatures increases the likelihood that the message will be marked as spam.

Please correct the SalesInbox software so that it is compliant with RFC2822 and messages signed with DKIM have their signatures preserved.