We've added ALIAS record monitoring to DNS Check.

An ALIAS record maps one DNS record to another of the same type. For example, you might use an ALIAS record to make the widgets.com A record resolve to the same IP address as the www.widgets.com A record:

ALIAS records have some similar use cases to CNAME records, with a few important differences:

DNS is incredibly flexible. One of the things that it allows you to do is enable load balancing and/or redundancy by creating multiple DNS records with the same name and record type. For example, you could create two A records for your company's domain name to perform round robin load balancing between two web servers. Another example is creating multiple MX records, so that failure of a single mail server doesn't take incoming email offline.

Unfortunately, this capability increases the complexity of monitoring DNS records, even if you're not intentionally using it. Having an extra, invalid DNS record could cause impaired performance, a service outage, or enable a man in the middle attack.

Today we're proud to announce an improvement to DNS Check which simplifies monitoring for these types of DNS issues.

The "Exclusive" Option

Each DNS record that's monitored by DNS Check has an "Exclusive" option which you can turn on and off:

When this option is turned on, DNS Check compares the full list of DNS records returned to the list of DNS records being monitored for the given record name / type combination. If the two sets of records match up exactly, the check passes. Otherwise, DNS Check will detect the error, and notify you about it.

This is an enhancement to DNS Check's previous functionality. The "Exclusive" option was initially released in May 2015, but was limited verifying that only one DNS record existed for a given name / type combination. Today's release removes the single record limitation. You can now specify that multiple "Exclusive" records should exist for the same name / type combination.

When the "Exclusive" option is turned off, DNS Check simply verifies that a DNS record exists with the value specified. It does not report any kind of error if additional records are returned.

We recommend turning the "Exclusive" option on whenever possible.

In April 2015 we launched DNS Check as a free service that allows you to monitor up to 10 DNS records for free, and get notified if any of them stop (or start) resolving to the values that you expect them to. This free service is now our "Basic" account type, and is still our most popular offering.

In May we added a paid tier which checks up to 100 DNS records at a time, and adds the ability to query custom name servers. This is known as our "Professional" account type.

Today we're proud to announce that we've added a new "Enterprise" account type to DNS Check. Enterprise accounts monitor up to 1,000 DNS records.

It's time to expand DNS Check's footprint, this time to Europe.

We just added a new name server hosted by Amazon Web Services in Ireland. The server's hostname is ireland1.dnscheck.co, and its IPv4 address is 52.48.61.155. No IPv6 address is assigned yet, although we plan to add one in.

This new name server joins our existing IPv4 and IPv6 capable name servers in New York and San Francisco.

We've made a number of updates to DNS Check's user interface to improve usability over the past couple weeks. Some of the more noteworthy updates are:

1. Added a search bar to the top of each DNS record type section. This allows you to search your monitored DNS records by name or value.

2. DNS records are now sortable by their pass/fail status, name, and value.

Today we're releasing two closely related features - the DNS Check API, and the DNS Check Integrations Directory. These features enable DNS Check to better integrate with third party services.

DNS Check API

The DNS Check API is REST API which enables checking on the status of monitored DNS records, and record groups.

We're proud to announce that DNS Check has integrated with Flowdock to provide reliable DNS record and name server monitoring with real-time notifications. This integration combines the strengths of DNS Checks's DNS monitoring service with Flowdock's chat service. It also allows you to receive notifications from DNS Check, coworkers, and and other monitoring systems through a common Flowdock interface.

Flowdock is a team collaboration app for desktop, mobile & web. Flowdock enables you chat, notify and share files in real-time.

DNS Check enables you to easily monitor, share and troubleshoot DNS records. You can import DNS your zone file and have DNS Check monitor the records in it, or specify individual records that you would like monitored.

You can designate that a DNS record is "exclusive," meaning it should be the only DNS record of its name / record type combination. For example, the MX record for your company's domain name should be the only MX record for that domain.

You have the option of making each set of DNS records publicly visible, or private, which can save precious seconds if a DNS record or name server is broken, but the person who maintains it doesn't normally have access to your monitoring system. Here's an example set of public DNS record checks.

We've developed a REST API which enables checking on the status of DNS records, and record groups that are monitored through DNS Check.

An example use case of the API is to augment monitoring systems that have limited DNS record checking capabilities. For example, many services support checking A and AAAA records, but lack support for checking MX and SPF records.

We plan to make the DNS Check API available to both free and paid accounts.

We just added a new feature which allows you to enable or disable notifications on a per DNS record group basis:

Prior to this update, notifications were permanently enabled for all DNS record groups. Now they're enabled by default, with the option to turn them off.

MX, or Mail Exchange records are DNS records that specify which mail servers are responsible for receiving email for a domain. When someone sends you an email, their mail server looks up the MX records for your domain (the part of the email address after the @ sign), and attempts to deliver the message to a mail server that's specified by those MX records.

If MX records are improperly configured, then legitimate email may not get delivered to you, and spam may find a way to bypass your spam filter's checks.

This post provides some background on how MX records work, followed by suggestions on how to check them.

MX Record Structure

Each domain name can have one or more MX records, and each MX record has two fields - the "Preference" and "Exchange".

Preference

An MX record's "Preference" value is a number between 0 and 65,535 which indicates how preferable that record is relative to other MX records for the same domain. If a domain only has one MX record, then the Preference doesn't matter. When more than one MX record exists for a domain, the MX record with the lowest Preference is checked to decide which "Exchange", or mail server to attempt to deliver mail to first.

Having the lower Preference win can seem counter intuitive, so the Preference is also sometimes called the MX record's "distance".

If two or more MX records tie for lowest Preference value, then the sending mail server randomly picks one for the first delivery attempt.

If the first delivery attempt fails, then the sender attempts to deliver the message to the MX record with the next lowest Preference. This process repeats until the sender either succeeds in contacting a mail server, or runs out of MX records to check.