Use ～と存じます in place of ～と思います when voicing your own opinion, assumption, or expectation toward a client or superior — above all in email, written reports, and formal meetings. 存じる is the humble (謙譲) verb for both 思う and 知る, so it lowers you, never the listener: don't use it about the other party's thoughts. The softened variants ～かと存じます and ～ものと存じます are the everyday workhorses of business correspondence.