Testing

Before exposing ports and validating DNS settings in Verify Proper Mail Configuration, ensure mail server is configured and running. See Configuration.

Verify Services Locked Down

Test SASL service.
telnet localhost 25
ehlo localhost

Note

Should see 250 auth plain login after issuing the ehlo command. This means that SASL dovecot is setup correctly.

Press ctrl + ] to quit.

Verify non-encrypted connections fail.
telnet localhost 143
telnet localhost 110
telnet localhost 995

Note

All unencrypted connections should fail with:

Unable to connect to remote host: Connection refused.

IMAP uses port 143.

POP uses ports 110, 995.

Verify IMAPS connections succeed.
openssl s_client -connect localhost:993

Note

Should get a * OK [{CAPABILITY LIST}] Dovecot ready. Verify the ceritificate listed is the correct Let’s Encrypt certificate for the domain used.

C logout {ENTER} to quit.

Verify encrypted SMTP connections succeed.
openssl s_client -starttls smtp -crlf -connect localhost:587

Note

Verify the certificate listed is the correct Let’s Encrypt certificate for the domain used.

crtl + c to quit.

Test Email Delivery

Ensure that users can receive mail. Test for users and alias cases.

Note

{USER} and {PASS} should be base64 encoded. Use a local utility if testing actual passwords.

Note

See testing outbound email via command line for additional instructions.

Telnet SMTP and send test emails.
telnet localhost 25
ehlo localhost
auth login
VXNlcm5hbWU6
{USER}
UGFzc3dvcmQ6
{PASS}
mail from: root@localhost
rcpt to: {USER}@{DOMAIN}
data
Subject: postfix text
testing mail from postfix
.
quit
Verify SSL/TLS SMTP can send.
openssl s_client -starttls smtp -crlf -connect mail.{DOMAIN}:587
ehlo mail.{DOMAIN}
auth login
VXNlcm5hbWU6
{USER}
UGFzc3dvcmQ6
{PASS}
mail from: root@localhost
rcpt to: {USER}@{DOMAIN}
data
Subject: postfix text
testing mail from SSL/TLS SMTP
.
quit

  • Should receive 220 from the server if working when initially connecting.

  • type ., {ENTER}, then quit to send mail.

  • Verify email sent is received (mail command works here). May also be verified by looking at the user’s maildir: /data/mail/data/{DOMAIN}/{USER}/new.

  • Also test email aliases and virtual addresses.

Verify Proper Mail Configuration

Tests must be green or the mail server will be blacklisted by major email services.

Use https://mxtoolbox.com to validate settings and ensure Ports (25,587) are exposed for testing.

  • Test {DOMAIN} and mail.{DOMAIN} MX records.

    • All results must be green.

    • The correct IP must be shown.

  • SMTP Test after looking up the MX record.

    • All results must be green, except PTR lookup.

Note

The PTR record maps an IP address to a DNS name. This is used by other mail servers to verify mail received from your server is a valid email.

This must be green if there is any intent to send mail to other services. Your ISP generally controls this, which implies that you have your ISP set this up for you or setup a hosted solution where you control the IP space.

PTR DNS Entry

Record

PTR

Name

{REVERSED IP OCTETS}.in-addr.arpa.

Target/Value/Data

mail.{DOMAIN}.

TTL

300 seconds