Some valid emails in log tagged "Accept; Defer disposition" appear to never arrive in the destination mailbox, what can be done?

Hello
1- If you're  runnnig 7.6x , you can use this CLI command:
       config system mailserver
           set delivery-tracking-status enable
       end

This setting enable logging of  specific delivery status of each email  (history log).
You will see  different status in red/green colours for each message such  Blocked, Failed, Queued,  Delivered etc

To locate the exact reason, try with right button on a individual message and do a "Cross Search" to obtain full details.

2-  I don't  understand completely your question: "whitelisting" a sender is something related to antispam layer; as you know, there' re another aspects or layer processing the mail that could trigger different dispositions.

3- Not the receiver I guess, maybe the sender could receive a notification message with info related. Look into docs for "Notification profiles"

regards

1. hello abelio, we have 7.6.x indeed, but the “mailserver” option  appears not available
    

   # config system 
    accprofile            configure system admin access group
    admin                 admin user configuration
    appearance            system appearance
    disclaimer-message    disclaimer customized message
    encryption            encryption
    fortiguard            fortiguard
    fortisandbox          fortisandbox configuration
    geoip-override        geographical location mapping for IP address(es) to override mappings from FortiGuard
    saml                  system saml configuration
    webfilter             webfilter
    webmail-language      set webmail language
   

   
   
   thanks for the “cross search” tip, didn,’t got wiser in this case, it appears to have passed everything.
    
2. I was not sure, I thought the whitelisting may just do a virus-check and skip the rest of the filtering process. Thanks for telling
    
3. Thanks,  I will look into this.

Could the logs show why a disposition was deferred and whether a configuration setting controls it? Also, can whitelisted senders/domains still be deferred, and could the recipient be notified with the reason when a mail is stuck in “Accept; Defer disposition.