Server retries to send mails way more often than 30 minutes

sending mail fails, it says retrying in 30min , but it did retry 2000 times in 1 hour
This did happen before the out of disk space segfault

Sample line of the log (they are all the same) :
2018-01-26 13:54:04: WARNING: Error sending mail to “paaa@aaa.net”. FTP: weird server reply(ec=8), Got unexpected smtp-server response: 554. Retrying in 30m

tail -n 10000 /var/log/urbackup.log| grep ‘2018-01-26 13’ | grep ’ WARNING: Error sending mail’ |wc -l
1953

Apparently it tries in batch (a count in each line for each minutes in the last 3 hours before the crash)

for NUM in {1…60} ; do tail -n 100000 /var/log/urbackup.log| grep “2018-01-26 11:$NUM” | grep ’ WARNING: Error sending mail’ |wc -l ; done
374
330
104
434
146
0
0
0
0
124
33
0
0
0
0
110
107
0
0
0
0
64
153
0
0
0
0
33
80
0
0
0
0
14
0
0
0
0
90
0
0
0
0
217
0
0
0
0
217
0
0
0
0
0
0
0
0
0
146
0
for NUM in {1…60} ; do tail -n 100000 /var/log/urbackup.log| grep “2018-01-26 12:$NUM” | grep ’ WARNING: Error sending mail’ |wc -l ; done
217
217
434
434
217
0
0
0
0
142
0
0
0
0
75
0
0
0
0
172
0
0
0
0
45
0
0
0
0
94
123
0
0
0
0
217
0
0
0
0
217
0
0
0
0
217
0
0
0
0
214
0
0
0
0
3
0
0
0
0
for NUM in {1…60} ; do tail -n 100000 /var/log/urbackup.log| grep “2018-01-26 13:$NUM” | grep ’ WARNING: Error sending mail’ |wc -l ; done
418
379
272
434
217
0
0
0
0
0
0
0
201
0
0
0
0
217
0
0
0
0
217
0
0
0
0
162
0
0
0
0
55
0
0
0
0
217
0
0
0
0
217
0
0
0
0
217
0
0
0
0
65
152
0
0
0
0
0
0

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.