The BOM is a two to four byte sequence at the start of an encoded file which tells the recipient if the characters are encoded using big-endian or little-endian byte order. In BizTalk generally the byte order mark is added when a file is UTF-8 or UTF-16 encoded using an XML assembler in a send pipeline. Sometimes applications cannot handle the initial bytes and you don’t want them to be added to your message. I recently read two articles about removing the Byte Order Mark (BOM) from outgoing messages in BizTalk 2006 one by Saravana Kumar and the other an official Microsoft KB article. Both of them recommend creating a custom pipeline with an XML assemble stage where the PreserveBom property is set to false. I find it a little strange that they don’t point out that you can accomplish this using the default XMLTransmit pipeline also. Just open the pipeline configuration in the Send Port properties and set PreserveBom to false… No custom Pipeline, no coding required.