The European Solar Telescope (EST) is a 4.2-m solar telescope, based on an aplanatic Gregorian configuration with an alt-azimuthal mount. This contribution presents the status of EST and describes the baseline for the preliminary design of the Telescope Structure (Telescope Mount), Enclosure and Pier. It also introduces the systems engineering, model and tools. In addition, it explains the rationale of the main specifications. The optical design has undergone major changes since the conceptual design. The M2 Assembly has become an Adaptive Secondary Mirror, the f-number has been changed and the number of optical surfaces has been reduced to 6 mirrors and 2 lens barrels. Therefore, part of the system has been updated and new assemblies have appeared: The Transfer Optics and Calibration Assembly (TOCA) and the Pier Optical Path (POP). Some requirements make this telescope unique: the primary mirror is above the elevation axis, the multi-conjugated adaptive optics is integrated in the telescope, the telescope instrumental polarization is minimized and the telescope will observe in open enclosure configuration to improve the natural air flushing. The drawback of the open configuration is that the telescope structure, M1 and M2 will be exposed to the wind load and the thermal load by radiation, forcing the development of a stiffer Telescope Structure, a specific thermal control to achieve the pointing and tracking performances and a low local seeing degradation. The Preliminary Design phase of the Telescope Structure, Enclosure and Pier have been developed by IDOM throughout 2021 and 2022, following technical requirements by the EST Project Office.