how to remove exim4 without removing mysql-server?

["cwinl-debian-user" <cwinl-debian-user@lnnu.edu.cn>]

Hi all

I want to remove exim4.
When I type 'apt-get --purge remove exim4-base' debian report:

mail2:/var/log# apt-get remove exim4-base
Reading Package Lists... Done
Building Dependency Tree... Done
The following packages will be REMOVED:
  exim4-base exim4-daemon-light mailx mysql-server
0 upgraded, 0 newly installed, 4 to remove and 0 not upgraded.
Need to get 0B of archives.
After unpacking 11.2MB disk space will be freed.
Do you want to continue? [Y/n]

But my mysql server shouldn't be remove.
how to remove exim4 without removing mysql-server?