If Outlook is slow finding the autodiscover records (This can be done in ex. through GPO’s in the Company), you may need to tell Outlook to exclude the root domain (As there we mostly find the company web page, not the autodiscover records) or other records.
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover\
DWORD: ExcludeHttpsRootDomain
Value: 1
The other records you can exclude, also under the Autodiscover key are as follows. Use a value of 1 to enable, delete the key if you no longer want to exclude these checks.
DWORD: ExcludeScpLookup
DWORD: ExcludeHttpsAutoDiscoverDomain
DWORD: ExcludeHttpRedirect
DWORD: ExcludeSrvRecord
How Autodiscover works:
https://msdn.microsoft.com/en-us/library/office/jj900169(v=exchg.150).aspx
