The access request feature allows people to request access to content that they do not currently have permission to see. As a site owner, you can configure the feature to send you mail when someone requests access to a site. You can then choose whether to approve or decline their request. If you approve the request, you can also specify the specific level of permission you’d like to assign to a user.
But, if you are in my case that I needed to configure the access request in all the web app, you can use the following PowerShell:
$spsites = get-spsite -Limit All foreach($spsite in $spsites) { foreach($SPweb in $spsite.AllWebs) { # if a site inherits permissions, then the Access request mail setting also will be inherited if (!$SPweb.HasUniquePerm) { write-host $SPweb "Inheriting from Parent site"; } elseif($SPweb.RequestAccessEnabled) { $SPweb.RequestAccessEmail = "mail@maildomain.com"; $SPweb.Update(); write-host $SPWEB "Configured" } } }
Hope it helps!