I use Postfix v3.1.15 to relay emails from my own internal systems (alerting, backup reports etc) to smtp.office365.com to be delivered to my O365 mailbox.
I've been using Postfix installed on Debian 9 for this for a couple of years. However I am receiving emails from Microsoft informing me of depreciation of TLS1.0 and TLS1.1 soon and to use TLS1.2 going forward as they have detected I am still using TLS1.0/TLS1.1.
Is there a simple command I can initially ascertain which version of TLS I am using currently? I am no Linux expert and each time I need to revisit anything Linux based I have to teach myself all over again as I do not administer Linux on a daily basis.
TY in advance...
My main.cf is as follows:
# See /usr/share/postfix/main.cf.dist for a commented, more complete version
# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
biff = no
# appending .domain is the MUA's job.
append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
readme_directory = no
# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
# fresh installs.
compatibility_level = 2
# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = debian.darnells.co.uk
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = $myhostname, debian.darnells.darnells.co.uk, localhost.darnells.darnells.co.uk, darnells.darnells.co.uk
relayhost = darnells-co-uk.mail.protection.outlook.com
# mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mynetworks = 192.168.0.0/20 192.168.40.5 192.168.30.5 192.168.20.5
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
