I just created a little statistic about rejections on my main
mailserver and found this:
# awk '/postfix\/postscreen.*550 5.5.1 Protocol error/ {print $8}'
/var/log/mail.log| awk -F: '{print $1}' | sort | uniq -c | sort -n |tail
--lines=25 | jdresolve --nostats --anywhere -
10 [57.77.85.136.bc.googleusercontent.com]
10 [178.233.148.34.bc.googleusercontent.com]
11 [241.135.114.136.bc.googleusercontent.com]
13 [213.102.87.34.bc.googleusercontent.com]
17 [249.70.67.136.bc.googleusercontent.com]
21 [204.57.148.34.bc.googleusercontent.com]
27 [146.58.7.34.bc.googleusercontent.com]
29 [38.185.196.104.bc.googleusercontent.com]
30 [154.107.171.34.bc.googleusercontent.com]
31 [176.63.255.35.bc.googleusercontent.com]
35 [223.62.231.35.bc.googleusercontent.com]
65 [226.229.139.34.bc.googleusercontent.com]
65 [161.204.21.34.bc.googleusercontent.com]
100 [194.122.83.34.bc.googleusercontent.com]
100 [5.13.221.35.bc.googleusercontent.com]
126 [70.164.91.34.bc.googleusercontent.com]
161 [234.118.158.34.bc.googleusercontent.com]
176 [189.95.80.34.bc.googleusercontent.com]
182 [87.147.169.34.bc.googleusercontent.com]
190 [215.90.245.35.bc.googleusercontent.com]
225 [158.215.197.104.bc.googleusercontent.com]
251 [126.237.23.34.bc.googleusercontent.com]
279 [255.183.66.136.bc.googleusercontent.com]
748 [254.181.148.34.bc.googleusercontent.com]
1382 [149.33.148.34.bc.googleusercontent.com]
This very much looks like crap, but WTF is going on?
2026-09-09T07:58:20.956152+02:00 mail-ccm-int postfix/postscreen[543022]:
NOQUEUE: reject: RCPT from [34.148.33.149]:59346: 550 5.5.1 Protocol error;
from=<[email protected]>, to=<[email protected]>, proto=SMTP,
helo=<evasia.net>
2026-09-09T07:58:22.612003+02:00 mail-ccm-int postfix/postscreen[543022]:
NOQUEUE: reject: RCPT from [34.106.79.140]:46528: 550 5.5.1 Protocol error;
from=<[email protected]>, to=<[email protected]>, proto=SMTP,
helo=<eurobunker-arena.com>
It's all using envelope sender addresses og "support@..."
--
Ralf Hildebrandt
Geschäftsbereich IT | Abteilung Netz | Netzwerk-Administration
Invalidenstraße 120/121 | D-10115 Berlin
Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
[email protected] | https://www.charite.de
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