  The Seyfert 1 galaxy Mrk841 was observed five times between 2001 and 2005 by
the XMM-Newton X-ray observatory. The source is well known for showing spectral
complexity in the variable iron line and in the soft X-ray excess. This paper
reports on the first study of Mrk841 soft X-ray spectrum at high spectral
resolution. The availability of multiple exposures obtained by the Reflection
Grating Spectrometer (RGS) cameras allows a thorough study of the complex
absorption and emission spectral features in the soft X-ray band.The three
combined exposures obtained in January 2001 and the two obtained in January and
July 2005 were analysed using the SPEX software. We detect a two-phase warm
absorber: a medium ionisation component (logxi~1.5-2.2 ergs s cm^{-1}) is
responsible for a deep absorption feature in the Unresolved Transition Array of
the Fe M-shell and for several absorption lines in the OVI-VIII band; a higher
ionisation phase with logxi~3 ergs s cm^{-1} is required to fit absorption in
the NeIX-X band. The ionisation state and the column density of the gas present
moderate variation from 2001 to 2005 for both phases. The high ionisation
component of the warm absorber has no effect in the Fe K band. No significant
velocity shift of the absorption lines is measured in the RGS data. Remarkably,
the 2005 spectra show emission features consistent with photoionisation in a
high density (n_e>10^{11} cm^{-3}) gas: a prominent OVII line triplet is
clearly observed in January 2005 and narrow Radiative Recombination Continua
(RRC) of OVII and CVI are observed in both 2005 data sets. A broad Gaussian
line around 21.7 Angstrom is also required to fit all the data sets. The
derived radial distance for the emission lines seems to suggest that the
photoionisation takes place within the optical Broad Line Region of the source.
