The requirement(s):

(1) Connect to Exchange via STMP and (2) basic authentication and send emails with a (3) custom From address to (4) recipients outside the domain.

I was able to get (1) - (3) working. I created a dedicated receive connector for this task and configured it like this:

Permissions:

• ms-Exch-SMTP-Accept-Any-Recipient (for authenticated users)
• ms-Exch-SMTP-Accept-Authoritative-Domain-Sender (for authenticated users)
• ms-Exch-SMTP-Accept-Any-Sender (for authenticated users)

Authentication:

• TLS
• Basic Authentication (without TLS)
• Exchange Server Authentication

However, I'm still struggeling with (4): I can send with "fake" From addresses to recipients inside the domain. Also, I can send with the original From address to recipients outside the domain.

Can you tell me what I'm missing, to configure Exchange to send emails with changed From addresses to recipients outside the domain? (Or is this even possible at all?) Thanks.

UPDATE

I have to correct myself: it seems to be working after all. There must be some issue with the mailbox I used for testing. It turned out it's working with other external mailboxes. However, I still have no idea what was different there... Anyways, you can take this as a documentation on how to configure Exchange in such a way ;)