email


Host or domain name not found. Name service error for name=smtp.gmail.com type=AAAA: Host not found, try again

Recently, a postfix mail server running on Ubuntu gave us the following error while trying to send an email to Bob:

Jun 16 17:02:03 gateway postfix/smtp[23522]: ED3799A0D27: to=[email protected], relay=none, delay=0.02, delays=0.01/0.01/0/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=smtp.gmail.com type=AAAA: Host not found, try again)

After several attempts like changing the protocol (inet_protocols) to IPv4 (since AAAA is an IPv6 A-record) in /etc/postfix/main.cf and so on we could not get it running.. We restored the configuration file to its original and then we restarted the service:

sudo service postfix restart;

It worked!…. no idea why..

Advertisements

Hikvision DVR sending email over GMail

Recently, we were trying to setup the email configuration of a Hikvision DVR which even though it was updated to the latest firmware we would get the message Testing Failed when trying to send an email over GMail.

In the GUI of the DVR there was an option to Enable SSL but no option to enable TLS/STARTTLS. So after consulting the GMail official documentation on how to configure an email client for GMail, we set the SMTP Port to 465 and enabled the SSL option. Then we created an application password for the DVR and tried to test the settings. To our disappointment we got the Testing Failed message.

After reading the latest user manual of the DVR, it mentioned an option to Enable SSL/TLS but not Enable SSL which got us curious. It raised the following question to us: “What if they enabled the TLS functionality but they forgot to update the GUI to match it?”. So we changed the port to 587 and hit Test again.

Guess what ?

It worked!!

It appears that Hikvision enabled the TLS/STARTTLS functionality but forgot to make their GUI reflect the change!

Using the settings depicted in this photo, we were able to send test messages from our Hikvision DVR over GMail using TLS/STARTTLS on port 587 of smpt.gmail.com!
The confirmation of the successful email sending operation.
“TESTING SUCCEEDED.”