A domain name, say foo.com, is registered to company ONE. The Address record of the DNS for that domain has been changed, to map foo.com with an IP which corresponds to a server of company TWO. Consequently, foo.com is now hosted to TWO, but the mail hosting is still done in the mail server of ONE. Since then, web access to mails under foo.com is not possible. What server actions between ONE and TWO should take place in order to restore mail web access?
Thank you in advance.
There is missing information in the question because there are multiple ways of moving hosting from ONE to TWO.
Assuming webmail was accessed with the typical webmail.foo.com simply altering the A record for foo.com (as stated in the question) should have no effect on the webmail.foo.com entry. Have nameservers for the domain been changed instead? (Seems likely if hosting change for foo.com broke a subdomain such as webmail.foo.com)
To fix the situation, you need to identify the correct IP address for the webmail service and enter an A record for webmail.foo.com using that IP as the value.
