Hi, Google Postmaster Tools recently started reporting that my TLS
configuration is not properly set up. I don't think anything has changed,
but perhaps it was never set up right. Here's what I'm seeing in the logs.

Sep 19 11:26:21 cipher postfix-gmail/smtp[1403397]: Untrusted TLS
connection established to gmail-smtp-in.l.google.com[64.233.177.27]:25:
TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange
X25519 server-signature ECDSA (prime256v1) server-digest SHA256

Here is my TLS configuration. I'm using SNI maps to deliver the cert
depending on one of two domains the user is accessing. The "combined" cert
below is the cert and key concatenated together.

smtp_tls_CAfile = /var/www/mail.example.com-443/ssl/DigiCertCA.crt
smtp_tls_loglevel = 1
smtp_tls_mandatory_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtp_tls_note_starttls_offer = yes
smtp_tls_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtp_tls_security_level = may
smtpd_sasl_tls_security_options = noanonymous
smtpd_tls_auth_only = yes
smtpd_tls_chain_files =
/var/www/mail.example.com-443/ssl/mail_example_com-2025.key,
/var/www/mail.example.com-443/ssl/mail_example_com-combined-2025.crt
smtpd_tls_exclude_ciphers = MD5, RC4, 3DES, IDEA, SEED, aNULL
smtpd_tls_loglevel = 1
smtpd_tls_mandatory_ciphers = high
smtpd_tls_mandatory_protocols = >=TLSv1.2
smtpd_tls_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_received_header = yes
smtpd_tls_security_level = may
tls_preempt_cipherlist = yes
tls_random_source = dev:/dev/urandom
tls_server_sni_maps = hash:/etc/postfix/vmail_ssl.map

I'm using TLS with submission on 587 and smtp on 25. Here is the openssl
output:

$ openssl s_client -connect mail.example.com:587 -starttls smtp -showcerts

submission
https://pastebin.com/FU2WwAbA

smtp
https://pastebin.com/2ZLp5dMD

Thank you,
Alex
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