I just ran through this process this past weekend (16.3.6885 to 100.0.6985)
My #1 WTF issue... make sure you have your LICENSE CODE HANDY as eventhough this is an upgrade, you will need to re-enter it otherwise you are stuck running in TRIAL MODE. I kid you not. I had to dig back through emails to locate it since the system has now been upgraded and you cannot just pull it off the licensing screen. A WARNING about this is all it would take in advance of running the update.
One other thing not listed in the instructions was after the upgrade is completed... be sure to do one final restart of the SmarterMail service (or a reboot of the server itself) I didn't at first and was ready to revert to my preconversion snapshot because sending and receiving messages was not working. Just on a whim restarted the SM Service ... poof! Everything started working.
Other than that, our 300ish domains and 3,000ish mailboxes all converted in about 10 minutes. (Your mileage may vary) with ZERO detected errors or warnings.
One thing I find odd, is that the convert_status page is STILL AVAILABLE days after I ran the conversion, but it no longer shows the convert time for each domain (which it does during the conversion and shortly after it), just now says "Up to date" for each domain. So I dunno if this is running its own updates at night or what, but something change the status displayed in that screen.
We have had a few issues since the update to 100.0.6985:
- Message Archive searching of anything but the current day is SLOW SLOW SLOW in fact it ended up chewing up my CPU to a point I needed to restart the SM service on a full archive search.
- Restarting SM service by itself (for the above issue) threw itself out of sync with ClamAV (thousands of failed connection scans as a result)
- I am seeing many different sorts of errors in the error log: The controller for path '/api/v1/mail/folder' was not found or does not implement IController ...... A potentially dangerous Request.Path value was detected from the client ........ Application Stopping. Reason: The hosting environment shut down the application...... (what app? I have no clue)
- I don't know that this is an "issue" but Mailbox Indexing now runs CONSTANTLY I forever have at least 200 mailboxes queued up and for some reason it leaves "Completed" items in the list seemingly randomly.
Aside from that, the system is running well for my users.
One "benefit" I've seen is my IMAP bandwidth usage has gone WAY WAY down... can't explain why but it used to peak around 2.3G per day, now it has been under 1G for each day since the upgrade... with no complaints from customers, so I am assuming it is all working... or I have a lot of customers on vacation. SMTP in/out seems to be about the same as from before the update but POP bw seems to have increased ever so slightly.