DKIM: signing failed

2018:10:15-04:55:49 r1 exim-in[5389]: 2018-10-15 04:55:49 exim 4.82_1-5b7a7c0-XX daemon started: pid=5389, no queue runs, listening for SMTP on port 25 (IPv4) port 587 (IPv4) and for SMTPS on port 465 (IPv4)
2018:10:15-04:56:00 r1 exim-out[17246]: 2018-10-15 04:56:00 Start queue run: pid=17246
2018:10:15-04:56:00 r1 exim-out[17246]: 2018-10-15 04:56:00 End queue run: pid=17246
2018:10:15-04:56:05 r1 exim-in[5389]: 2018-10-15 04:56:05 SMTP connection from [192.168.5.2]:40664 (TCP/IP connection count = 1)
2018:10:15-04:56:05 r1 exim-in[17257]: 2018-10-15 04:56:05 [192.168.5.2] F=<info@my-nas.ru> R=<test@gmail.com> Accepted: from relay
2018:10:15-04:56:05 r1 exim-in[17257]: 2018-10-15 04:56:05 1gBs73-0004UL-2R ctasd reports 'Unknown' RefID:str=0001.0A0C0211.5BC3F3B5.0045,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0
2018:10:15-04:56:05 r1 exim-in[17257]: 2018-10-15 04:56:05 1gBs73-0004UL-2R <= info@my-nas.ru H=(mail.my-nas.ru) [192.168.5.2]:40664 P=esmtp S=821 id=fe99c6e193d17283854a5bd03a4f2cd6@localhost
2018:10:15-04:56:05 r1 exim-in[17257]: 2018-10-15 04:56:05 SMTP connection from (mail.my-nas.ru) [192.168.5.2]:40664 closed by QUIT
2018:10:15-04:56:07 r1 smtpd[5163]: QMGR[5163]: 1gBs73-0004UL-2R moved to work queue
2018:10:15-04:56:10 r1 smtpd[17265]: SCANNER[17265]: 1gBs78-0004UT-CZ <= info@my-nas.ru R=1gBs73-0004UL-2R P=INPUT S=17
2018:10:15-04:56:10 r1 smtpd[17265]: SCANNER[17265]: id="1000" severity="info" sys="SecureMail" sub="smtp" name="email passed" srcip="192.168.5.2" from="info@my-nas.ru" to="test@gmail.com" subject="dfghfdgh" queueid="1gBs78-0004UT-CZ" size="17"
2018:10:15-04:56:10 r1 smtpd[17265]: SCANNER[17265]: 1gBs73-0004UL-2R => work R=SCANNER T=SCANNER
2018:10:15-04:56:10 r1 smtpd[17265]: SCANNER[17265]: 1gBs73-0004UL-2R Completed
2018:10:15-04:56:11 r1 exim-out[17271]: 2018-10-15 04:56:11 1gBs78-0004UT-CZ DKIM: signing failed (RC -101)
2018:10:15-04:56:16 r1 exim-out[17268]: 2018-10-15 04:56:16 1gBs78-0004UT-CZ => test@gmail.com P=<prvs=08262cb35a=info@my-nas.ru> R=dnslookup T=remote_smtp H=mxs.mail.ru [94.100.180.104]:25 X=TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256 C="250 OK id=1gBs7E-0007Ke-09"
2018:10:15-04:56:16 r1 exim-out[17268]: 2018-10-15 04:56:16 1gBs78-0004UT-CZ Completed