Intermolecular dipole-dipolar relaxation is considered in the framework of Redfield equations describing the evolution of the spin density matrices for multicomponent solutions. Two types of contribution from intermolecular dipole–dipolar interactions are identified. Contributions of the first type can be emulated using the external random field (ERF) model, while contributions of the second type cannot. The latter are responsible for relaxation coupling between solute and solvent, and can be expressed in terms of cross-relaxation rates. A complete system of Redfield equations for multicomponent liquids is not practical due to its size and the multitude of unknown parameters. For this reason, interpretation of experimental data usually is limited to the ERF model, even if unreliable for experiments where solvent spins are exposed to the effect of pulses. As an alternative, it has been suggested that complete system of Redfield equations can be truncated so that the solvent part is limited to spin polarizations. Solvent multispin modes are ignored as insignificant from the point of view of solute relaxation. So formulated, this approach is referred to as the ‘coupled solute solvent relaxation’ (CSSR) model. The validity of this approximation is examined using the examples of AX–AB and AX–ABX type binary mixtures. The elements of complete Redfield matrices embracing both solute and solvent are calculated. The results include cross-correlations between intermolecular dipolar interactions, which are calculated for spherical molecules with off-centre spin sites. Simulations indicate that the CSSR approach provides a very accurate approximation, regardless of the inherently complex nature of solvent relaxation and the existence of several potential paths for intermolecular magnetization transfer. It offers improvement over the ERF model, particularly in the evaluation of intermolecular contributions, in the case when both solute and solvent spins come under the effect of RF pulses during the course of experiments.