upgrade alpine v3.11->3.12.1, dovecot v2.3.9.3->2.3.11.3, socat v1.7.3.3->1.7.3.4
https://github.com/dovecot/core/releases/tag/2.3.10
https://github.com/dovecot/core/releases/tag/2.3.10.1
https://github.com/dovecot/core/releases/tag/2.3.11.3
http://www.dest-unreach.org/socat/doc/CHANGES