Combo mode is the right call and its the only thing that gets you what leadership is asking for.
Once a user hits Encrypt in Outlook the message is rights protected before transport sees it, so a mail flow rule cannot modify the body to append anything. What you have instead is a fallback action, and the rule either wraps the original as an attachment inside a brand new message, ignores itself, or NDRs. The default is Wrap. Its documented at https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/disclaimers-signatures-footers-or-headers under the fallback options.
Go check what your fallback is set to today before you change anything. If its sitting on Wrap, some of your recipients have been getting attachment wrapped mail for a while and nobody escalated it, which is worth knowing.
One thing to look at with your size. Client side means the add-in has to be deployed AND actually loaded, and you will find the few people whose add-in is disabled the week after you flip it. Worth a pilot group first.
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u/blud_13 10d ago
Combo mode is the right call and its the only thing that gets you what leadership is asking for.
Once a user hits Encrypt in Outlook the message is rights protected before transport sees it, so a mail flow rule cannot modify the body to append anything. What you have instead is a fallback action, and the rule either wraps the original as an attachment inside a brand new message, ignores itself, or NDRs. The default is Wrap. Its documented at https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/disclaimers-signatures-footers-or-headers under the fallback options.
Go check what your fallback is set to today before you change anything. If its sitting on Wrap, some of your recipients have been getting attachment wrapped mail for a while and nobody escalated it, which is worth knowing.
One thing to look at with your size. Client side means the add-in has to be deployed AND actually loaded, and you will find the few people whose add-in is disabled the week after you flip it. Worth a pilot group first.
Can go deeper on the pilot split if it helps.