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SMTP Server says "Queued for Delivery", but Email Never Arrives

May 16 '16 at 08:59

Would appreciate if you can shed some light on why does the log show that emails are not sent – instead they say “Queued mail for delivery”? According to the User (of my software), the email never goes out. This is happening (suddenly) to ALL their outgoing SMTP emails using Chilkat.

For example:

      SmtpCmdSent: DATA<CRLF>
      SmtpCmdResp: 354 Start mail input; end with <CRLF>.<CRLF>
    mimeDataSize: 234098
    smtpSendData: Elapsed time: 0 millisec
      SmtpCmdSent: <CRLF>.<CRLF>
      SmtpCmdResp: 250 2.6.0 <x> [InternalId=x, Hostname=x] Queued mail for delivery
    smtpFinalResponse: Elapsed time: 281 millisec
    smtpConversation: Elapsed time: 281 millisec


The SMTP client (such as Chilkat, Mozilla Thunderbird, etc.) is responsible for "handing off" the email to the SMTP server for delivery (either to a local mailbox, or to a remote mailbox where the SMTP server acts as a relay). The SMTP client's task is ended when the SMTP protocol exchange is completed, and the SMTP server says "OK, I've got it and I'll take it from here.". That's what's happening here: The SMTP server says "Queued for delivery", meaning that it's received everything from the SMTP client (Chilkat) successfully, will deliver the email. If the email never actually gets delivered, then the problem is downstream of the Chilkat-->SMTP server handoff. In other words, you'll need to investigate the SMTP server, it's settings, etc. to see what's going on with it.