Hello @Tyler
>Is the same issue happening with IMAP accounts?
We have pretty much Connector-only environment. There are couple of IMAP users, but with non-Outlook email clients
>Where the rules working correctly at some point and suddenly stopped?
No, rule are new. But I (kind of) remember trying to use Outlook rules couple of years back with similar results and after failing to get them work properly I've switched to IMAP filters in MDaemon.
>Where the rules exported from another Outlook client and Imported in this client or were they created manually?
No. Created from scratch in this particular Outlook.
>Is the "Upgrade Now" button available in the Rules > Manage Rules & Alerts > Options menu?
No. Greyed out.
>Is the issue only occurring for this specific account?
No, I'm using 3 (Connector) accounts, it is happening in all of them. All 3 accounts are in the same Outlook though (1 personal and 2 admin accounts)
>If you have access to other versions/bit versions of Outlook...
As I've mentioned above, I tried this couple of years back (with Outlook 2013 and Connector v5 or v6, don't remember exactly), because in pre-Connector times I've used Outlook rules quite a lot. Had a couple of users who also relied heavilly on the Rules and gave them up (but I don't know why, actually. Could be something non-related, this was never reported to me as an issue).
I am using Outlook 2019 now and until yesterday, couple of hours before posting in the Forum, with Connector v7.0.7, 64-bit. Rules were setup couple of days ago.
>I configured a simple rule to route messages from a specifc sender to sub-folder.
After some more testing last couple of days, 3 test rules, simple deleting messages based on sender/subject I've noticed that if messages arrive while Outlook is not up (working), upon Outlook start, messages are never processed. When I start Outlook, wait minute or 5 minutes or 10, messages which should be affected by the rules remain in Inbox. If I run the rules manually, messages are deleted.
If Outlook is already openned when messages meeting the rule criterias arrive, rules seem to work in let's say 90% of the time. For the remaining 10% I cannot figure out why they are not processed.
>I would also check the Add-ins.

Or, from the Report
Add-Ins count : 8
01 Add-In GUID :{EFEF7FDB-0CED-4FB6-B3BB-3C50D39F4120} Status: ACTIVE Description : Microsoft SharePoint Server Colleague Import Add-in
02 Add-In GUID :{6E4D2D00-9CC0-4B4A-B6FF-25D1135C33FF} Status: ACTIVE Description : MDaemon Connector
03 Add-In GUID :{799ED9EA-FB5E-11D1-B7D6-00C04FC2AAE2} Status: ACTIVE Description : Microsoft VBA for Outlook Addin
04 Add-In GUID :{93E5752E-B889-47C5-8545-654EE2533C64} Status: ACTIVE Description : OneNote Notes about Outlook Items
05 Add-In GUID :{2163EB1F-3FD9-4212-A41F-81D1F933597F} Status: ACTIVE Description : Outlook Social Connector 2016
06 Add-In GUID :{47D635E3-9D14-40C9-A28C-64C2AA7AF647} Status: ACTIVE Description : Symantec Endpoint Protection Outlook Add in
07 Add-In GUID :{2D702E20-B8A1-4C0B-A218-32223CE86EA1} Status: inactive Description : TeamViewer Meeting Add-In
08 Add-In GUID :{F959DBBB-3867-41F2-8E5F-3B8BEFAA81B3} Status: ACTIVE Description : Microsoft Exchange Add-in
>Try disabling all plug-ins except the MDaemon Connector Add-in, restart Outlook, verify all Add-ins are still disabled, and see if your rules begin to process.
Tried disabling Symantec add-in only first, then the all together (without Connector, of course). No difference.
>Commenting on beta versions would be premature at this point as revisions are not yet final.
Understood. Just thought you might have something already
In the meantime I've found MSG file in User_Mail_Storage\MDConfiguration.IMAP, in winmail.dat format, but wasn't able to extract anything making any sense to me from it.
Thank you