Original Title: "error code: 5305.7.0"ISP is Sympatico, occasionally response emails originating with and directed back to source origin using O.E. generates error report: Msg could not be sent because the Sender's email address was rejected. Server response: Protocol SMTP 5305.7.0 Must issue a STARTTLS command first! Q: "Where to issue it, and what is the protocol?

If you're using Outlook Express, you must be using Windows XP. If that's the case, your question belongs in http://social.answers.microsoft.com/Forums/en-US/xpnetwork/threads, not here.Brian Tillman [MVP-Outlook]--------------------------------https://mvp.support.microsoft.com/profile/Brian.TillmanIf a reply helps, please vote it as helpful. If a reply solves the issue, please mark it as an answer.