Sticky mail function
Mails set to sticky will be displayed in the sticky area of the mailing list, and the sticky area is at the top of the post office list, so that users can quicklyOpen and view important messages. Currently, up to 5 messages are supported as sticky messages.

Method of operation:
1) In the mail list, select the mail that needs to be topped, and click the \"Mark\" option in the navigation bar, as shown below:

2) You can also directly click the top icon in the mail list to perform the top operation, as shown below:
