Small and medium enterprises (SMEs) typically rely on emails to interact with other SMEs in a collaborative network. However, with the use of different document standards and interpretation techniques establishing a shared understanding of business documents (or emails) can be difficult and raise interoperability issues. In this paper we introduce Commius - a zero cost enterprise system that aims to achieve seamless interoperability among collaborative SMEs. At the heart of Commius is a semantic alignment mechanism capable of automatically interpreting a document received by the system. However, when the automatic interpretation fails, Commius employs agent-inspired negotiation techniques to help achieve common understanding of the document with other Commius system (installed at sender or collaborative SME). This paper presents details of Commius's email negotiation mechanism with the help of a running scenario that demonstrates how Commius-based negotiation can support SMEs achieve semantic alignment in collaborative networks. © 2011 IEEE.