Can a workflow change the sender address on email threads?
No. There is no workflow action that changes or overrides the sender address on an email thread.
How Plain picks the sender address
Plain replies from the address the customer originally wrote to. If you have several alternate addresses set up, such as mailbox1@company.com and mailbox2@company.com, each reply goes out from whichever address the inbound email arrived on, not from a fixed default. You manage alternate addresses in Settings, under Email.
You can pick a different configured address in the reply composer before you send. There is no way to automate this switch with a workflow.
What workflows can do
- Add a note recording which mailbox a thread arrived on, such as "Received via mailbox1".
- Apply labels, set priority, assign a team member, or route the thread based on the inbound address.
- Send automated follow-up messages from the workspace default address or the address inferred from the thread.
Workaround
If every reply must go out from one specific address regardless of which mailbox it arrived in, select that alternate address in the reply composer for each thread. There is no automated equivalent.