What's Exim retry time when outgoing mail encounters a 421 "Service not available - too busy"

My WHM > Tweak Settings > Email delivery retry time is set to 15 m When sending a mail out sometime the server gets a 421 "Service not available - too busy", hence Exim queues the message. From my understanding Exim should retry after 15 min, instead in these two examples he retries after about 50 min (at 15:19 then at 16:09 / at 15:21 then at 16:09) Why does it take so much before retrying? [QUOTE] root@js [~]# exigrep "joe@alice.it" /var/log/exim_mainlog 2020-03-13 15:19:31 1jCl9v-00087c-FP <= help@mydomain.com H=(W764BIT) [151.41.210.200]:20021 P=esmtpsa X=TLSv1.2:ECDHE-RSA-AES256-SHA384:256 CV=no A=dovecot_login:help@mydomain.com S=7164 id=4C7AA2FD41524BC6B3EEF60FE00B10D0@W764BIT T="Re: Hello form Florida" for joe@alice.it 2020-03-13 15:19:31 1jCl9v-00087c-FP Sender identification U=mydom D=mydomain.com S=help@mydomain.com 2020-03-13 15:19:31 1jCl9v-00087c-FP SMTP connection outbound 1584109171 1jCl9v-00087c-FP mydomain.com joe@alice.it 2020-03-13 15:19:32 1jCl9v-00087c-FP == joe@alice.it R=dkim_lookuphost T=dkim_remote_smtp defer (-44) H=smtp.aliceposta.it [82.57.200.133]: SMTP error from remote mail serverafter RCPT TO:: 421 Service not available - too busy 2020-03-13 16:09:21 1jCl9v-00087c-FP Sender identification U=mydom D=mydomain.com S=help@mydomain.com 2020-03-13 16:09:24 1jCl9v-00087c-FP => joe@alice.it R=dkim_lookuphost T=dkim_remote_smtp H=smtp.aliceposta.it [82.57.200.133] C="250 <5E57C6B80487D695> Mail accepted" 2020-03-13 16:09:24 1jCl9v-00087c-FP Completed 2020-03-13 15:21:13 1jClBZ-0008AE-P8 <= info@mydomain.com H=(W764BIT) [151.41.210.200]:20042 P=esmtpsa X=TLSv1.2:ECDHE-RSA-AES256-SHA384:256 CV=no A=dovecot_login:info@mydomain.com S=7996 id=8E8A4002D4DB42A0B6DFD09C14AD5D29@W764BIT T="Fw: Hello form Florida" for joe@alice.it 2020-03-13 15:21:13 1jClBZ-0008AE-P8 Sender identification U=mydom D=mydomain.com S=info@mydomain.com 2020-03-13 15:21:13 1jClBZ-0008AE-P8 SMTP connection outbound 1584109273 1jClBZ-0008AE-P8 mydomain.com joe@alice.it 2020-03-13 15:21:14 1jClBZ-0008AE-P8 == joe@alice.it R=dkim_lookuphost T=dkim_remote_smtp defer (-44) H=smtp.aliceposta.it [82.57.200.133]: SMTP error from remote mail serverafter RCPT TO:: 421 Service not available - too busy 2020-03-13 16:09:24 1jClBZ-0008AE-P8 Sender identification U=mydom D=mydomain.com S=info@mydomain.com 2020-03-13 16:09:25 1jClBZ-0008AE-P8 => joe@alice.it R=dkim_lookuphost T=dkim_remote_smtp H=smtp.aliceposta.it [82.57.200.133] C="250 <5E340AC20B970F77> Mail accepted" 2020-03-13 16:09:25 1jClBZ-0008AE-P8 Completed