On a domain, in the DNS settings is an SRV record named:
_autodiscover._tcp
and value is:
0 10 443 autodiscover.*hostname*.net.
What is it and what does it do?
I am migrating websites to a new server and I need to know how this will work with the new server on a different host.
SRV DNS records allow the use of DNS for publishing services and service discovery. Their main use is to allow services to run easily on non-standard ports and to reduce the configuration burden when setting up clients.
A SRV record has the following form:
_Service._Protocol.Name. TTL Class SRV Priority Weight Port Target
Service: the symbolic name of the service.
Protocol: the transport protocol of the service; this is usually either TCP or UDP.
Name: the domain name terminated with a . for which this record is valid - often omitted in DNS shorthand which then defaults to the zone name.
TTL: standard DNS time to live field.
Class: standard DNS class field (this is always IN for Internet).
Priority: the priority of the target host, lower value means more preferred.
Weight: A relative weight for records with the same priority.
Port: the TCP or UDP port on which the service is to be found.
Yours appears an example of an autodiscovery service :) pointing to TCP port 443 on the aptly named host autodiscover.*hostname*.net.
One such autodiscovery service seems to be used in automatically configuring MS Outlook but that may not be the only use-case.
The autodiscover and autoconfig DNS records makes it easier to connect an email client to a mail server.
If you use Thunderbird, when you set up a new mail account you'll see an option to automatically detect mail server settings for that mail server's domain, e.g. its SMTP(S) and POP3(S) or IMAP(S) settings. Using the _autoconfig._tcp record these settings can then be automatically applied to the outgoing and incoming emails respectively for that new email account - saving a user the bother of checking the protocols and ports involved in this process.
If your email client is Outlook, a similar process occurs but this uses the _autodiscover._tcp record.
