On the last leg of migrating from Exchange to Smartermail and thought I would post these as there's likely to be others in a similar position. I accept that this may not scale well, but for smaller setups, may be of help.

Migration tool
I have been using the Exchange migration tool to import from an onprem Exchange. With the help from Tony, I found out it uses EWS. To get the tool to talk to the outgoing server directly (assuming SM is on a different IP and you are running the two servers side by side), on Exchange, set the ECP / EWS virtual directory / internal URL to the server IP. mine was to the hostname. Then under IIS, go to EWS, then SSL settings and untick the Require SSL option, apply and restart IIS. I found that the certificate was also stopping the migration but since it's no longer web facing the SSL isn't needed. Then migrate per user

Transport Rules to Content Filter
I have a lot of transport rules, these go back over 10 years (as a backup to spam filters for those that get through) and I need to get them into SM. As there's no import option, what I have done is...

Export the rules out of Exchange, powershell..

$file = Export-TransportRuleCollection

Set-Content -Path "C:\Temp\TransportRules.xml" -Value $file.FileData -Encoding Byte

I copied the XML to the desktop. Open.

Save a blank text file on the desktop and open. What you are doing is copying the relevant sections into the text file. they will appear as 'zzz', 'yyy', 'xxx' etc. Save the text file, you can keep notepad open

Open excel, open the txt file, import wizard, delimited on comma then finish. Now we need to clean the columns, so go to find and select then replace. in Find add a 'space' and a 'apostrophe', The box below 'replace with' is empty and click replace all, then repeat with just a apostrophe (no space). this removes the formatting marks.

Select all the items, copy. Then in a cell below, right click, paste special but use the transpose option, this makes the copy go down. Recopy the items and paste into the content filter. If the text fails to copy correctly, check for any spaces at the beginning of the keywords

I use exceptions to each rule so that safe email addresses or email domains are bypassed.. 

    General

         ALL conditions must be met

    Conditions

        Contains specific words or phrases / subject or body / contains (list of keywords)

        Contains specific words or phrases / from email address / does not contain (list of emails / domains)

    Action

        I fwd any to a spam mailbox in case of false positives

It only takes a few minutes to do once you figure out the process.

Hope these help :)