This is easy to verify on clean Debian 7 (without mysql-* installed): 

...
Setting up exim4-daemon-heavy (4.80-7) ...
[....] Starting MTA:/usr/sbin/exim4: /usr/lib/libmysqlclient.so.18: no version information available (required by /usr/sbin/exim4)
/usr/sbin/exim4: /usr/lib/libmysqlclient.so.18: no version information available (required by /usr/sbin/exim4)
/usr/sbin/exim4: /usr/lib/libmysqlclient.so.18: no version information available (required by /usr/sbin/exim4)
[ ok 4.

Just did the following:

root@debian7:~# fc -l
...
54       apt-get install percona-server-server-5.5 percona-server-client-5.5
55       mysql -uroot -proot
56       which mysql
...
66       apt-get install exim4-daemon-heavy
root@debian7:~# ldd /usr/lib/libmysqlclient.so.18
        linux-gate.so.1 =>  (0xb7777000)
        libpthread.so.0 => /lib/i386-linux-gnu/i686/cmov/libpthread.so.0 (0xb7465000)
        libssl.so.1.0.0 => /usr/lib/i386-linux-gnu/i686/cmov/libssl.so.1.0.0 (0xb740d000)
        libcrypto.so.1.0.0 => /usr/lib/i386-linux-gnu/i686/cmov/libcrypto.so.1.0.0 (0xb724d000)
        libdl.so.2 => /lib/i386-linux-gnu/i686/cmov/libdl.so.2 (0xb7249000)
        libm.so.6 => /lib/i386-linux-gnu/i686/cmov/libm.so.6 (0xb7223000)
        librt.so.1 => /lib/i386-linux-gnu/i686/cmov/librt.so.1 (0xb721a000)
        libc.so.6 => /lib/i386-linux-gnu/i686/cmov/libc.so.6 (0xb70b7000)
        /lib/ld-linux.so.2 (0xb7778000)
        libz.so.1 => /lib/i386-linux-gnu/libz.so.1 (0xb709d000)
root@debian7:~# ldd /usr/sbin/exim4
/usr/sbin/exim4: /usr/lib/libmysqlclient.so.18: no version information available (required by /usr/sbin/exim4)
        linux-gate.so.1 =>  (0xb7705000)
        libresolv.so.2 => /lib/i386-linux-gnu/i686/cmov/libresolv.so.2 (0xb75d3000)
        libnsl.so.1 => /lib/i386-linux-gnu/i686/cmov/libnsl.so.1 (0xb75bc000)
        libcrypt.so.1 => /lib/i386-linux-gnu/i686/cmov/libcrypt.so.1 (0xb7589000)
        libm.so.6 => /lib/i386-linux-gnu/i686/cmov/libm.so.6 (0xb7563000)
        libpam.so.0 => /lib/i386-linux-gnu/libpam.so.0 (0xb7554000)
        libdb-5.1.so => /usr/lib/i386-linux-gnu/libdb-5.1.so (0xb73c2000)
        libldap_r-2.4.so.2 => /usr/lib/i386-linux-gnu/libldap_r-2.4.so.2 (0xb7370000)
        liblber-2.4.so.2 => /usr/lib/i386-linux-gnu/liblber-2.4.so.2 (0xb7360000)
        libmysqlclient.so.18 => /usr/lib/libmysqlclient.so.18 (0xb7072000)
        libpq.so.5 => /usr/lib/libpq.so.5 (0xb7047000)
        libsqlite3.so.0 => /usr/lib/i386-linux-gnu/libsqlite3.so.0 (0xb6f97000)
        libsasl2.so.2 => /usr/lib/i386-linux-gnu/libsasl2.so.2 (0xb6f7b000)
        libperl.so.5.14 => /usr/lib/libperl.so.5.14 (0xb6df1000)
        libdl.so.2 => /lib/i386-linux-gnu/i686/cmov/libdl.so.2 (0xb6ded000)
        libpthread.so.0 => /lib/i386-linux-gnu/i686/cmov/libpthread.so.0 (0xb6dd4000)
        libc.so.6 => /lib/i386-linux-gnu/i686/cmov/libc.so.6 (0xb6c71000)
        libgnutls.so.26 => /usr/lib/i386-linux-gnu/libgnutls.so.26 (0xb6ba8000)
        libpcre.so.3 => /lib/i386-linux-gnu/libpcre.so.3 (0xb6b69000)
        /lib/ld-linux.so.2 (0xb7706000)
        libgcrypt.so.11 => /lib/i386-linux-gnu/libgcrypt.so.11 (0xb6ae4000)
        libssl.so.1.0.0 => /usr/lib/i386-linux-gnu/i686/cmov/libssl.so.1.0.0 (0xb6a8c000)
        libcrypto.so.1.0.0 => /usr/lib/i386-linux-gnu/i686/cmov/libcrypto.so.1.0.0 (0xb68cd000)
        librt.so.1 => /lib/i386-linux-gnu/i686/cmov/librt.so.1 (0xb68c4000)
        libkrb5.so.3 => /usr/lib/i386-linux-gnu/libkrb5.so.3 (0xb67f1000)
        libcom_err.so.2 => /lib/i386-linux-gnu/libcom_err.so.2 (0xb67ec000)
        libgssapi_krb5.so.2 => /usr/lib/i386-linux-gnu/libgssapi_krb5.so.2 (0xb67ae000)
        libtasn1.so.3 => /usr/lib/i386-linux-gnu/libtasn1.so.3 (0xb679c000)
        libz.so.1 => /lib/i386-linux-gnu/libz.so.1 (0xb6783000)
        libp11-kit.so.0 => /usr/lib/i386-linux-gnu/libp11-kit.so.0 (0xb6770000)
        libgpg-error.so.0 => /lib/i386-linux-gnu/libgpg-error.so.0 (0xb676c000)
        libk5crypto.so.3 => /usr/lib/i386-linux-gnu/libk5crypto.so.3 (0xb6742000)
        libkrb5support.so.0 => /usr/lib/i386-linux-gnu/libkrb5support.so.0 (0xb6739000)
        libkeyutils.so.1 => /lib/i386-linux-gnu/libkeyutils.so.1 (0xb6734000)