The molecular mobility of polyepoxy networks synthesized from diglycidyl ether of bisphenol-A (DGEBA) and cured with aliphatic diamines featuring varying polypropylene glycol (PPG) backbone lengths was investigated. The influence of ambient storage conditions, notably absorbed moisture, in conjunction with the network crosslink density on physical properties, was explored by using multiple techniques, including differential scanning calorimetry, dielectric and mechanical spectroscopies. In addition to known effects on glass transition and its dynamic manifestations, significant effects on secondary relaxation modes were observed, further highlighting the importance of controlling initial sample conditions when conducting molecular mobility studies. A bimodal β-relaxation was observed in the presence of absorbed moisture as a result of an additional water-related mode, β2 , ascribed to hydroxyether groups interacting with water.