1) How do I know which servers are used to search for keys with gpggpg --search-key <keyword> 2) How to add a server to the list of queried server?
GPG key server for key search?
postfix
Reputable key servers exchange key updates with others, so using one is the same as using another (with slight delays in some cases). You should use the sks server pool, ideally using a secure connection; see the previous link for details, or this answer. The short version isgpg --keyserver pool.sks-keyservers.net --search-key ...(As of GPG 2.1 this is the default configuration.)You can store the keyserver setting permanently by adding the relevant option to ~/.gnupg/dirmngr.conf:keyserver hkps://hkps.pool.sks-keyservers.netYou can specify multiple keyserver options in that file, but I get the impression that only the last one is taken into account.To actually answer your initial question, at least version 2.1 of GPG shows the key server used for a query:$ gpg --search-key A36B494Fgpg: data source: https://host-37-191-236-118.lynet.no:443...