Letter From an Unknown Woman

2001 TV movie

Cast: Irene Jacob, Christopher Thompson, Karlheinz Hackl, Joachim Bißmeier, Nina Proll, Patricia Hirschbichler, Klaus Rott et al.
Screenplay: Jean-Claude Carriére
Director: Hu Mei, Jacques Deray
Production: SK-Film/Kirchmedia/Progefi for France 3 and ORF

IMDb

Synopsis:
Vienna around 1930: One night, writer Albert Rank receives a letter from a stranger and is deeply moved by it. It is the confession of a woman who has dedicated her entire life to her love for him.