Hi Linulex,
actually, your question is not only reasonable, but as well up-to-date to meet the new service-port assignments, made by IANA for RFC conformity ( last updated
18.11.2016 => http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt ), where port 465 has been assigned to the service "
urd"
( tcp ) and the service "
igmpv3lite"
( upd ).
The definite answer to your question:
Would it be wise/possible/safe to close port 465 (smtps) in the firewall?
... is "
YES" (
wise/
possible and
safe ), when you use SMTP-MSA on your server(s) on port 587.
But ( and here comes the culprit...
), if you do that, you have no possible fail back, in case of communication issues between MUA or/and MTA, which could raise support requests due to ( possible ) communications errors from your customers, who use standard settings at their mail - clients ... unfortunately,
no mail - client has the standard
POP3s- port - setting "
465/995", but use instead the
POP3 - port - setting "
25/110", which will take a looooooong time, untill this changes.