SysAdmin Pro email setup not working

New v16 install, restored a backup from v13. Went through the usual bit of editing generic to rewrite the sending address. The issue is that postfix is not using the SMTP server specified in SysAdminPro email config.
Setting:
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Connection attempt:
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This varies between the two domain controllers in the org; it’s trying to send email to the Active Directory domain name, which resolves to one of two domain controllers, instead of what’s in the SMTP server field. Spent hours trying to make it behave last night. Any ideas?

Did you restart just in case? I can’t remember if that’s required for this kind of change to take affect.

Yes, we did. Over and over and over. The problem went away when we conceded and opened the support VPN with an agreement that nothing would be changed. They connected and 60 seconds later the apply button resulted in the settings in the GUI being used, but support claimed they hadn’t changed anything. Hmmm.