diff --git a/README.md b/README.md
index e4094a9..ea7f9b8 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ sizeable network of people with email servers thanks to this script.
 I've linked this file on Github to a shorter, more memorable address on my
 website so you can get it on your machine with this short command:
 
-```
+```sh
 curl -LO lukesmith.xyz/emailwiz.sh
 ```
 
@@ -21,7 +21,7 @@ give your full domain without any subdomain, i.e. `lukesmith.xyz`.
 
 - **Postfix** to send and receive mail.
 - **Dovecot** to get mail to your email client (mutt, Thunderbird, etc.).
-- Config files that unique the two above securely with native log-ins.
+- Config files that link the two above securely with native log-ins.
 - **Spamassassin** to prevent spam and allow you to make custom filters.
 - **OpenDKIM** to validate you so you can send to Gmail and other big sites.
 
@@ -128,4 +128,10 @@ support me at [lukesmith.xyz/donate](https://lukesmith.xyz/donate.html).
   [this site](https://mxtoolbox.com/blacklists.aspx) to see if it is. Don't
   worry if you are: sometimes especially new domains are automatically assumed
   to be spam temporarily. If you are blacklisted by one of these, look into it
-  and it will explain how to remove yourself.
+  and it will explain why and how to remove yourself.
+- Check your DNS settings using [this site](https://intodns.com/), it'll report
+  any issues with your MX records
+- Ensure that port 25 is open on your server.
+  [Vultr](https://www.vultr.com/docs/what-ports-are-blocked) for instance
+  blocks this by default, you need to open a support ticket with them to open
+  it. You can't send mail if 25 is blocked
diff --git a/emailwiz.sh b/emailwiz.sh
index eaa0f92..a5e7727 100755
--- a/emailwiz.sh
+++ b/emailwiz.sh
@@ -38,7 +38,7 @@ apt install postfix dovecot-imapd dovecot-sieve opendkim spamassassin spamc
 # Check if OpenDKIM is installed and install it if not.
 which opendkim-genkey >/dev/null 2>&1 || apt install opendkim-tools
 domain="$(cat /etc/mailname)"
-subdom="mail"
+subdom=${MAIL_SUBDOM:-mail}
 maildomain="$subdom.$domain"
 certdir="/etc/letsencrypt/live/$maildomain"
 
@@ -66,6 +66,15 @@ postconf -e "smtpd_use_tls = yes"
 postconf -e "smtpd_tls_auth_only = yes"
 postconf -e "smtp_tls_security_level = may"
 postconf -e "smtp_tls_loglevel = 1"
+postconf -e "smtp_tls_CAfile=$certdir/cert.pem"
+postconf -e "smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1"
+postconf -e "smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1"
+postconf -e "smtpd_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1"
+postconf -e "smtp_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1"
+postconf -e "tls_preempt_cipherlist = yes"
+postconf -e "smtpd_tls_exclude_ciphers = aNULL, LOW, EXP, MEDIUM, ADH, AECDH, MD5,
+                            DSS, ECDSA, CAMELLIA128, 3DES, CAMELLIA256,
+                            RSA+AES, eNULL"
 
 # Here we tell Postfix to look to Dovecot for authenticating users/passwords.
 # Dovecot will be putting an authentication socket in /var/spool/postfix/private/auth
@@ -127,6 +136,9 @@ echo "# Dovecot config
 ssl = required
 ssl_cert = <$certdir/fullchain.pem
 ssl_key = <$certdir/privkey.pem
+ssl_min_protocol = TLSv1.2
+ssl_cipher_list = ALL:!RSA:!CAMELLIA:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!SHA1:!SHA256:!SHA384:!LOW@STRENGTH
+ssl_prefer_server_ciphers = yes
 ssl_dh = </usr/share/dovecot/dh.pem
 # Plaintext login. This is safe and easy thanks to SSL.
 auth_mechanisms = plain login
@@ -235,7 +247,7 @@ chmod g+r /etc/postfix/dkim/*
 # Generate the OpenDKIM info:
 echo "Configuring OpenDKIM..."
 grep -q "$domain" /etc/postfix/dkim/keytable 2>/dev/null ||
-echo "$subdom._domainkey.$domain $domain:mail:/etc/postfix/dkim/mail.private" >> /etc/postfix/dkim/keytable
+echo "$subdom._domainkey.$domain $domain:$subdom:/etc/postfix/dkim/$subdom.private" >> /etc/postfix/dkim/keytable
 
 grep -q "$domain" /etc/postfix/dkim/signingtable 2>/dev/null ||
 echo "*@$domain $subdom._domainkey.$domain" >> /etc/postfix/dkim/signingtable