upgrade alpine base image from v3.14.2 to v3.14.3 including postfix package upgrade from v3.6.2-r0 to v3.6.3-r0 (see below)
http://www.postfix.org/announcements/postfix-3.6.3.html
https://git.alpinelinux.org/aports/commit/main/postfix?id=0eda017cd4a34f823b54bbaeaa088e1520c78016