I have recently changed web hosting companies for my website. I’m planning to go live in the next day or two. I know that I need to change the DNS record so that it points to my new web server. Is there anything I need to do regarding email DNS? My web hosting company says “if you manage the DNS for your domain [which i do], your DNS should be setup as follows.” It shows a list like this:
I don’t know what this is. I need to make sure my email comes through to my existing email addresses when the site goes live. What do I need to do to make sure all email comes through when the switch is made?
The best you can do is lower the TTL (Time-To-Live) of all your current DNS entries to a low value like 300 (seconds, i.e., 5 minutes), so DNS servers may only cache the IP of your domain for 5 minutes and have to re-ask again after that.
Then when you switch you can be more-or-less* your change will propagate over the internet in a matter of minutes instead of hours, or indeed days.
Some email might still arrive at the old server during this switch, so be sure to check this for another day or two days or so.
TTL is a hint and not something that must be followed, so some DNS servers completely ignore TTL (and take a large value instead, to avoid data traffic)
These are your mail records or Mail eXchange records. As long as your email supplier is zmta.sitewebhost.com. your fine. otherwise you will need to amend your DNS to match the information they have given you.
A CNAME is a Change Name record its like re-writing the place its going to.
So mywebmail.site.com will actually go to zwebmail.sitewebhost.com but will still appear as the original name.
Just set up your domain like they told you. It will be fine
I do recommend reducing your TTL as per @rpkamp said. this is good advice and will mean if there is any problem you will be able to deal with it with a minimum of downtime.
This brings me to my next question. Once the DNS is changed, how would my clients check their email on the old server? Tech support said something about checking via IP address. How can we check email via IP address?
If you are running Windows on your computer then the simplest way is to apply a temporary change in the hosts file to point your domain back to the old hosting. Your computer will then access the old hosting directly instead of doing a domain name lookup on the web and finding the new hosting.
As per previous, this will allow you to temporarily override your clients DNS from his workstation or server. Get the old mail and then you can remove it and go back to the new mail pointing.
Just be aware this is like a very slow switch. Best thing to do is make the change, wait 24 hours then check the old mail once.
Mail will either go to the old or new place and “worst case” scenario for DNS is 48 hours. 24 hours for everyone in the worlds DNS server to update, 24 hours for the caches to update. In reality this is probably the most conservative you can get. 90% of the dns servers and caches will update within a few hours at worst.
In honesty my DNS normally updates within a few seconds.
Some DNS take several weeks to update - most update within a few minutes but you have absolutely no control over any except the one your domain is registered with (which updates instantly when you change it).
In 12 years of working with an ISP I haven’t heard of any DNS servers taking that long. Where are you getting that information?
Are you talking about a core DNS servers, I’m not talking about bobs DNS server in the basement here, I’m talking about ISPs/TLD hosts.
And whilst I appreciate what you are saying about control. ISP’s and TLD hosts have a responsibility to update their DNS and provide up to date information.
There is a legal responsibility to provide the correct route as well, you could effectively sue someone for providing the wrong route and stopping your business from operating as a result.
Anyone giving the wrong route for that long should have their routing circumvented by the people on either side.
I have seen it actually happen on one occasion when I moved my hosting and where I was using DNS tools to monitor the change. One or two of the DNS that got picked at random by the tools for checking were still pointing at the old hosting a couple of weeks after all the others had switched over.
About four years ago. Can’t remember which countries they were in but they were not countries you’d associate with being very technology minded. I suppose they figured that updating every two or three weeks ought to be good enough given that without those DNS the people in their country would probably have no internet access at all.
