The modern-looking Mallard train offers wireless internet, increased leg-room, new carriage interiors and improved catering services.
The mailing will be sent to a 170,000-strong database, which includes companies with a £10 million-plus turnover within the catchment area of GNER stations.
The work will break at the end of October and will support a regional cinema, TV and press advertising campaign developed by Vallance Carruthers Coleman Priest.
Anthony Carr, the group account director at Clark McKay & Walpole, said: "Our below-the-line campaign incorporates the spirit of the above-the-line creative and contributes to a truly integrated campaign."
The mailing was written by Jim Archer and art directed by Dan Plotkin.