There is only one location to blacklist natively in Domino and that is [Server configuration document] - [[Router/SMTP tab] - [ Restrictions and controls] - [SMTP Inbound controls]
Even when using an IMAP client, IMAP only applies to you downloading mail, when you send mail, it always goes over port 25-SMTP.
You might have multiple configuration documents, often it is hard to tell which one applies to a server, this is the order in which config documents are applied:
1. Doc that have the server name entered
2. Doc with group name that contains the server - if multiple groups, the alphabetically first applies
3. Docs for Wildcard entries (e.g. */ou/o). The first wildcard entry in the list that would apply to the server is used
4. Default configuration document
Be aware that config docs are NOT cumulative, the server goes through the list as indicated above and uses the first one it can find that would apply.
If none of this applies, it is not Domino that is blacklisting you but rather something else, some anti-spam or AV SW on the server that is intercepting the call on port 25. Check for this by verifying if in the [Server document] - [Ports tab] - [Internet ports] - [Mail subtab] SMTP inbound is set to port 25 or something else.
