The example file ssmtp.conf.sample does not at all mention either STARTTLS or authentication for target MTAs, something which I assume is needed by many people.
Would it be a good idea to at least add, in comments, an indication thereof? Something along these lines, maybe:
--- ssmtp.conf.sample 2019-11-15 16:44:44.000000000 +0000
+++ ssmtp.conf.sample.new 2019-12-12 14:18:53.946701000 +0000
@@ -41,3 +41,11 @@
# If you want to have debugging of the config file parsing, move this option
# to the top of the config file and uncomment
+# Use these parameters for securely authenticating against your
+# mailhub; check ssmtp.conf(5) for further details.
I'd also like to point out that the home page for ssmtp as recorded at  is
no longer valid and seems to have moved to https://packages.qa.debian.org/s/ssmtp.html