Hi @Xiao Chang (常潇) ,
Welcome to Microsoft Q&A forum.
Please note that currently Microsoft Q&A only support posting in English.
Could you please edit your question into English? Then we can better understand the question and help you with this issue, thanks for your understanding.
The following is my understanding of your question and some suggestions. If I misunderstood your question, please feel free to correct me.
Is the mail system you are currently using Exchange online?
If so ,you could refer to the following steps to grant the “send on behalf” permission:
1. In the Exchange admin center, go to Recipients > Groups.
2. Select the group that you want to allow users to send on behalf of.
3. Select Settings > Edit manage delegates.
4. In the Add a delegate section, enter the email address of the user that you would like to have Send as access.
5. Select Permission Type as Send on behalf from the drop-down.
6. Select Save changes.
Then you can create a new message, select the group as the sender in the from input box.
Hope the above suggestions are helpful to you!
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