RE: SMTP Email Missing Sender
Hello,
Unfortunately, I am not entirely sure what you mean with Sender is missing. Is there a specific error where this is stated? Are you using Office 365 as the mail server and BC is in SaaS. If you cannot figure out what the cause is, then feel free to raise it to Microsoft support via your partner or CSP or via your company if you are a partner. Especially when using SaaS, we can easily look up the telemetry.
Before raising this issue to Microsoft, ensure you note the tenant ID (or Office 365 domain name), environment name like Sandbox / Production or if there are multiple PRODUS, company name and the time stamp the customer did test the scenario / reproduced the issue so we can easily track it. This will make your support experience as efficient as possible so we do not have to ask for that info.
Thanks a lot!