Error in /var/log/exim4/mainlog

2017-06-28 11:53:21 exim 4.84_2 daemon started: pid=13291, -q30m, listening for SMTP on [127.0.0.1]:25 [::1]:25
2017-06-28 11:53:21 Start queue run: pid=13292
2017-06-28 11:53:21 1Xf0lB-0000Iv-AZ cancelled by timeout_frozen_after
2017-06-28 11:53:21 1Xf0lB-0000Iv-AZ Completed
2017-06-28 11:53:21 End queue run: pid=13292
2017-06-28 12:00:06 exim 4.84_2 daemon started: pid=14119, -q30m, listening for SMTP on [127.0.0.1]:25
2017-06-28 12:00:06 Start queue run: pid=14120
2017-06-28 12:00:06 End queue run: pid=14120
2017-06-28 12:00:34 1dQ9ly-0003fu-TU <= root@test.example.com U=root P=local S=461
2017-06-28 12:00:37 1dQ9ly-0003fu-TU ** me@example.org R=dnslookup T=remote_smtp X=TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128 DN="C=US,ST=California,L=Mountain View,O=Google Inc,CN=mx.google.com": SMTP error from remote mail server after end of data: host aspmx.l.google.com [2607:f8b0:4001:c12::1a]: 550-5.7.1 [2a01:4f8:c17:754a::2] Our system has detected that this message does\n550-5.7.1 not meet IPv6 sending guidelines regarding PTR records and\n550-5.7.1 authentication. Please review\n550-5.7.1  https://support.google.com/mail/?p=IPv6AuthError for more information\n550 5.7.1 . 130si1521589iou.178 - gsmtp
2017-06-28 12:00:37 1dQ9m1-0003fz-0W <= <> R=1dQ9ly-0003fu-TU U=Debian-exim P=local S=1796
2017-06-28 12:00:37 1dQ9ly-0003fu-TU Completed
2017-06-28 12:00:37 1dQ9m1-0003fz-0W => /var/mail/mail <root@test.example.com> R=mail4root T=address_file

Insert

disable_ipv6=true

in /etc/exim4/exim4.conf.template.

Example:

...

######################################################################
#                    MAIN CONFIGURATION SETTINGS                     #
######################################################################

# Just for reference and scripts. 
# On Debian systems, the main binary is installed as exim4 to avoid
# conflicts with the exim 3 packages.
exim_path = /usr/sbin/exim4

disable_ipv6=true

# Macro defining the main configuration directory.
# We do not use absolute paths.
.ifndef CONFDIR
CONFDIR = /etc/exim4
.endif

...

• https://hasin.me/2015/11/03/how-to-disable-ipv6-for-exim4-with-vesta-panel/