We give a characterization of those abelian groups which are direct sums of cyclic groups and the Jacobson radical of their endomorphism rings are closed. A complete characterization of p-groups A for which (EndA, T L ) is locally compact, where T L is the Liebert topology on EndA, is given. We prove that if A is a countable elementary p-group then EndA has a non-admissible ring topology. To every functorial topology on A a right bounded ring topology on EndA is attached. By using this topology we construct on EndA a non-metrizable and non-admissibe ring topology on EndA for elementary countable p-groups A.1991 Mathematics Subject Classification. Primary: 16W80, 16A65, 16S50, 16N40.Key words and phrases. topological ring, Jacobson radical, quasi-injective module, endomorphism ring, admissible topology, Bohr topology, Liebert topology, finite topology, functorial topology, shift homomorphism.The research was supported by FAPESP (Brazil) Process N: 2014/18318-7, CNPq (Brazil) and RFFI (Russia) 13-01-00239a.