There are our server logs:
###
4m 12K 1e1Uul-003IoE-G8 <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

3m 12K 1e1UvA-003J0n-GC <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

3m 12K 1e1Uvj-003JFi-29 <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

3m 2.3K 1e1Uvl-003JJj-VG <> *** frozen ***
root@chi-rs31.websitehostserver.net

3m 2.3K 1e1Uvm-003JJy-7c <> *** frozen ***
root@chi-rs31.websitehostserver.net

2m 12K 1e1Uvw-003JOn-00 <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

1m 12K 1e1UxB-003Jzx-No <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

1m 12K 1e1UxT-003K9O-JP <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

1m 12K 1e1Uxe-003KEy-3H <> *** frozen ***
lpfcom@chi-rs31.websitehostserver.net

2017-10-09 05:06:58 1e1Uxe-003KEy-3H <= <> R=1e1UxY-003KBm-9C U=mailnull P=local S=11962 T="Mail delivery failed: returning message to sender" for lpfcom@chi-rs31.websitehostserver.net
2017-10-09 05:06:58 cwd=/var/spool/exim 3 args: /usr/sbin/exim -Mc 1e1Uxe-003KEy-3H
2017-10-09 05:06:58 1e1Uxe-003KEy-3H Sender identification U=mailnull D=-system- S=mailnull
2017-10-09 05:06:58 1e1Uxe-003KEy-3H ** lpfcom@chi-rs31.websitehostserver.net R=fail_remote_domains: The mail server could not deliver mail to lpfcom@chi-rs31.websitehostserver.net. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries.
2017-10-09 05:06:58 1e1Uxe-003KEy-3H Frozen (delivery error message)

2017-10-09 05:06:52 1e1UxY-003KBm-9C <= lpfcom@chi-rs31.websitehostserver.net U=lpfcom P=local S=10397 T="Pandora Factory Outlet 80% OFF" for deudeuchman@orange.fr
2017-10-09 05:06:52 cwd=/var/spool/exim 3 args: /usr/sbin/exim -Mc 1e1UxY-003KBm-9C
2017-10-09 05:06:52 1e1UxY-003KBm-9C Sender identification U=lpfcom D=lpf.com.cy S=lpfcom
2017-10-09 05:06:52 1e1UxY-003KBm-9C SMTP connection outbound 1507543612 1e1UxY-003KBm-9C lpf.com.cy deudeuchman@orange.fr
2017-10-09 05:06:58 1e1UxY-003KBm-9C ** deudeuchman@orange.fr R=lookuphost T=remote_smtp H=smtp-in.orange.fr [80.12.242.9] X=TLSv1:DHE-RSA-AES256-SHA:256 CV=yes: SMTP error from remote mail server after end of data: 550 5.2.0 Mail rejete. Mail rejected. ofr_506 [506]
2017-10-09 05:06:58 cwd=/var/spool/exim 7 args: /usr/sbin/exim -t -oem -oi -f <> -E1e1UxY-003KBm-9C
2017-10-09 05:06:58 1e1Uxe-003KEy-3H <= <> R=1e1UxY-003KBm-9C U=mailnull P=local S=11962 T="Mail delivery failed: returning message to sender" for lpfcom@chi-rs31.websitehostserver.net
2017-10-09 05:06:58 1e1UxY-003KBm-9C Completed
###

Also, we've found the following malicious files:
###
/home/lpfcom/public_html/pub/docs/model/search/reports/public/formlist.php
/home/lpfcom/public_html/wp-content/languages/mo.php
/home/lpfcom/public_html/funcs/info.php
###

Please provide us with your WAN IP address and we will allow access to your account from that address only. Thus you will have the ability to take appropriate measures.Here is the link to find out what your WAN IP is: http://myip.is/. Looking forward to hearing from you.