We have outsourced the mail services to the mail service provider and service provider has placed one linux box in our LAN for fetching. In the domain control panel details are set as below:
1. MX is pointing to the mail service provider
2. A record is pointing to the mail.mydomain.com # mail.mydomain.com is placed in our LAN.
All the users email client is configured with “A” record details that is hosted in the LAN, also all the mobile black berry users are also configured with the A record details that is hosted in the LAN.
Now due to the change in the ISP service type, so for using IP address has to be changed but this change will affect our mail services for the email client users also for the blackberry users we have around 80 blackberry users.
Hence I have scheduled this activity of changing this IP address in the router or firewall on the weekend, Following have to be done:
1.Login to the domain control panel and replace the existing IP address to the new IP address.
2.Configure the router/firewall with the new IP address, In the router/firewall NAT one of the public ip to the private ip address of the linux mail box (mail.mydomain.com)
3.Public IP in the A record for mail.mydomain.com and in the router/firewall natted IP aaddress should be same.
When did nslookup or dig TTL values are 86400 please give me is there any best practice can done so that mail services down time will be very much minimal, we cannot afford to the long time for the dns replication due to this mail services getting affected. Please help me in this with the best possible practice step by step. Thanks in advance.