?
Solved

Multiple MX Records

Posted on 2011-04-20
6
Medium Priority
?
771 Views
Last Modified: 2012-05-11
why is it that when performing a query with dig (linux) for a domain's MX records do some of them come back with multiple MX records and each point to different IP's? The only thing I can think of is for disaster recovery and back-up. Is there something other meaning to this? I typically see this with companies that have their email hosted by third party.  Thanks in advance.
0
Comment
Question by:J-Vas
6 Comments
 
LVL 74

Expert Comment

by:Glen Knight
ID: 35434485
If it's a hosting provider they will have multiple connections & IP's for redundancy, therefore will require an MX for each SMTP entry point.
0
 
LVL 3

Expert Comment

by:saigasmith
ID: 35436658
It also allows for priority as each MX record has a priority (lower the number, higher the priority). The MX record with the highest priority is the actual target computer where mail boxes are located. The other MX records designate the backup computers in case the actual target computer is not accissible. They store the e-mails temporarily, and periodically attempt to redirect e-mails to the actual target computer.

0
 
LVL 74

Expert Comment

by:Glen Knight
ID: 35436739
Sorry, but that's not strictly true.

The priority does not necessarily mean the lowest number is where the mailboxes are stored.

They could be stored at both, or both routes could go to the same place just for different ISP's/IP addresses as used for redundancy.
0
Has Powershell sent you back into the Stone Age?

If managing Active Directory using Windows Powershell® is making you feel like you stepped back in time, you are not alone.  For nearly 20 years, AD admins around the world have used one tool for day-to-day AD management: Hyena. Discover why.

 
LVL 7

Expert Comment

by:BWaring
ID: 35438087
Some additional notes on priority... priority just indicates the order that the various mail servers should be contacted;  the lower number is a higher priority. So if three mail servers have priorities of 10, 20 and 30, try the 10 server first, if that fails, try the 20 server, and if that fails try the 30 server... what constitutes failure and when to try the next higher preference server is not necessarily the same in all SMTP gateway implementations....

Anyway, more info on MX records can be found here: http://en.wikipedia.org/wiki/MX_record
0
 

Author Comment

by:J-Vas
ID: 35457371
Just to make sure, there is no other meaning to multiple MX records for a domain? Even if not using a  third party hosting company?
0
 
LVL 7

Accepted Solution

by:
BWaring earned 500 total points
ID: 35457455
More than one MX record means more places to deliver mail. Start at higher priority (lower number) and work from there. If two priorities are the same, then alternate (gateway dependent). That's it. Those rules can work themselves in to many 3rd party/non-3rd party scenarios regarding primary delivery, overflow delivery, redundancy, capacity planning, etc...

If you have a specific example or issue you are concerned about, let us know...

For example, you could have more than one mail gateway at different edges of you WAN, accepting mail for your domain. Each of these could have the same priority. If either is down, the other will be used.... one example... there are many more....
0

Featured Post

Hire Technology Freelancers with Gigs

Work with freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely, and get projects done right.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

With so many activities to perform, Exchange administrators are always busy in organizations. If everything, including Exchange Servers, Outlook clients, and Office 365 accounts work without any issues, they can sit and relax. But unfortunately, it…
Steps to fix “Unable to mount database. (hr=0x80004005, ec=1108)”.
The video tutorial explains the basics of the Exchange server Database Availability groups. The components of this video include: 1. Automatic Failover 2. Failover Clustering 3. Active Manager
The basic steps you have just learned will be implemented in this video. The basic steps are shown to configure an Exchange DAG in a live working Exchange Server Environment and manage the same (Exchange Server 2010 Software is used in a Windows Ser…
Suggested Courses
Course of the Month13 days, 19 hours left to enroll

809 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question