In the world of the email router, incoming and outgoing profiles were separate, so one user or queue could have separate email servers. Let’s say you wanted incoming email to come from exchange, but you wanted to send outgoing email via SMTP, you could do it.
With the deprecation of the email router, the only option is server-side sync. With server-side sync, the incoming and outgoing email settings are on the mailbox record, and there is only one mailbox per user or queue.
So what to do if you want email to come in via Exchange and go out via SMTP or or some other connection?
One additional approach is set up two different queues and associate the email address with both queues. the “in” queue is only set up for server-side sync for incoming email and associated with an email server profile for your exchange server. The “out” queue is set only set up for server-side sync for outgoing and associated with an email server profile for your SMTP server.
When an email comes in, it may still go to the “out” queue, since it matches by email address. To prevent this, simply create a real time workflow that creates a queue item when an item is added for the “out” queue, adding the item to the “in” queue. This will make any items added to the “out” queue get moved to the “in queue.
Then, when you send your responses to items in the “in” queue, select the “out” queue as the “from.”
If it confuses users to see two queues, only give them access to the in queue and use a real time workflow to change the “from” on emails sent from the “in” queue to the “out” queue.