Chimera Computing Ltd


Mail Delivery FAQ


Also see the Delivery Failures and Mail Flow section.
  • Mail sent to Exchange server just disappears!
  • This maybe an issue with ISA server SMTP filtering corruption. When using filtering based on Exchange > Global Settings > Message Delivery > Filtering, if the message comes from a blocked sender/domain, the SMTP server responds with "554 5.1.0 Sender Denied", and it rejects the message. Messages filtered by the ISA filter are received by the SMTP server, scanned, submitted to adv.q., and then dropped

    (this information was taken from an exchange forum, see this link for more information)
  • Why do senders get non-deliverable replies sent but email delivers ok?
  • Email delivery from EFS is working fine, however ever sender is getting a non-deliverable reply (NDR) back similar to the following (in this example, the domain you are accepting mail for is "")

    This is an automatically generated Delivery Status Notification.

    Delivery to the following recipients failed.

    If this is happening for every sender, then chances are the email address in the NDR is your catch-all account email address. In some cases, the domain name in your catch-all email address is the same as what EFS accepts mail for (usually, the catch all email address will be something like and therefore will not be picked up by EFS) For instances where the catch-all email address is in the same domain (such as in the example above) it will therefore exist in the message headers and be picked up as a valid address by EFS (even though the message was not actually sent to that address by the sender) EFS then sends to the actual recipient and the catch-all account, the catch-all account does not exist so a non-deliverable reply is sent back to the sender. To resolve, you need to tell EFS to ignore the catch-all account. Under the Aliases tab, add the catch-all email address (in this example, then tick the "Ignore Email Address" and add it to the list. EFS will now ignore any instance of the catch-all email address in inbound messages.
  • How does EFS process mail recipients for delivery of a message?
  • EFS first searches the standard mail header fields, To: Cc: Bcc: and Received: headers. ('Received' usually occurs if the message is from a mailing list) If no recipients for your domain are found, the message will be addressed to the postmaster (assuming you have not setup custom headers) Messages are sent to the postmaster generally when a message is either "copied" into your account by your ISP (ie: the headers contain no address of the recipients email address) or EFS is misconfigured by not using the correct custom headers. To resolve this, temporarily turn off mail forward from the SMTP section then allow EFS to check a few messages. Open one of the retrieved .MSG files from the \E.F.S\Inbox folder in Notepad. Look through the top of the message for email addresses in your domain and make note of the corresponding "header" name (eg: X-Rcpt-To:) Add this header to the Headers section of EFS and (optionally) disable EFS from checking the To: field. For more information, see Mail comes in but only goes to the Postmaster, what's happening?
  • Why do I occasionally get malformed messages sent to the postmaster?
  • Click here for detailed information
  • Under what conditions will the Postmaster get mail?
  • The postmaster only ever gets sent a message from EFS if:

    - EFS can not find your domain anywhere in the message header - thus being unable to determine who the final recipient(s) are. This generally occurs if the message is either "copied" into your account from your service provider or the message is junk/spam mail.

    - The message has an invalid message header (possibly invalid characters or an invalid mail address that the server can not resolve or faults on) the message is temporarily moved to the "Errors" folder, the rest of the messages are sent (if any), the connection is re-established and the malformed message is sent to the postmaster. If EFS fails on addressing the postmaster, the message is moved to the 'Junk' folder.

    -You have "BCC all messages to" checked under the Aliases section and have specified the postmaster account

    - (also see "How EFS handles BCC'd mail")
  • Mail comes in but only goes to the Postmaster, what's happening?
  • This generally will be due to one of the following:

    1. You have misspelled your domain name
    Check the spelling and ensure your domain name is correct under the SMTP section of EFS. Also ensure that you are NOT using virtual domain aliasing (VdA) if you do not require it. To ensure it is turned off, click the VdA button from the Domains tab then click Cancel to disable VdA.

    2. Messages contain recipients addresses in headers other than To: and From:
    This will be dependant on your ISP's mail server. For example, NTMail actually puts the users address in a field other than the To: and From: fields (which EFS uses to look for recipients of your domain). NTMail creates new fields X-Originally-To: and X-Originally-From: which hold the desination and sending email addresses.

    You can either ask your ISP or check this yourself by viewing the headers of one of the mail messages that has been addressed to the postmaster (If you're using Outlook, double click the message then choose View, Options and look down the headers box for the intended recipient of that message) You can tell EFS to check in this field instead of the normal To: and From: fields. Under the Headers section in EFS, click to add custom headers to the list and optionally bypass the To:, Cc:, Bcc: and Received: headers
    This is not an EFS error.  EFS forwards mail to an SMTP server for recipients it finds in a message. If that recipient does not exist on the mail server, then it is up to the mail server to send an NDR (non-deliverable) reply back to the sender. If you would like copies of "NDR" messages to go to the postmaster, you can simply set this up in Exchange. To do this: 

    - Exchange 5.5:  Properties of Internet Mail Service, "Internet Mail" tab, click the "Notifications" button 
    - Exchange 2000: Properties of your Virtual Server, "Messages" tab, add an entry to "Send a copy of NDR's to" 

    NOTE: Its always best to ensure you're running the latest Exchange Service Pack (at time of writing, the latest are Exchange 5.5 SP4 and Exchange 2000 SP3)
  • How does EFS handle BCC'd mail?
  • Blind carbon copy (BCC) messages don't always contain a BCC: field in the header. Instead, the recipient is sometimes contained in one of the "Received:" fields (and is hidden at the client level) Since EFS handles mailing lists (where the address of the mailing list is generally in the "To:" field and the intended recipient is in one of the "Received:" headers) then BCC mail is automatically handled as well (although never guaranteed). However, some ISPs mail servers try to be a little more secure - when they receive a BCC'd message, the message is placed into your account but any reference to the actual BCC address is stripped from the message making it impossible for EFS to determine the recipient it's intended for. In this case, the postmaster would receive the message.


    (Chimera Computing Ltd)