Plesk postfix mail send failure to resend behavior. Handling of resend mail queue.

Category：Plesk

Pub.date：2018-05-13

## Dwell time when sending mail fails

Plesk 17.8.11 Long dwell time when sending mail fails.

## Initial value

The default behavior of postfix from mail sending failure to resending was as follows.

```
queue_run_delay = 100s
minimal_backoff_time = 300s
maximal_backoff_time = 4000s
maximal_queue_lifetime = 5d
bounce_queue_lifetime = 5d
```

1.If sending fails, put it in deferred. 
2.Check for deferred every queue_run_delay (100 seconds). 
3.Resend any mail that exceeds the minimal_backoff_time (300 seconds). 
If it fails again, resend after twice the time (300 x 2 = 600 seconds). 
If it fails again, resend after 4 times the time (300 x 4 = 1200 seconds). 
4.Repeat until maximal_backoff_time (4000 seconds) is exceeded. 
If it fails again, resend at this time interval. 
5.Give up resending if maximal_queue_lifetime (5 days) is exceeded. 
6.If bounce_queue_lifetime (5 days) is exceeded, an error mail is returned to the sender.

In other words.
```
300s	(After 5 minutes)
600s	(After 10 minutes)
1200s	(After 20 minutes)
2400s	(After 40 minutes)
4000s	(1 hour, 6 minutes, 40 seconds later)
8000s	(2 hours, 13 minutes, 20 seconds later)
12000s	(3 hours and 20 minutes later)
16000s	(4 hours, 26 minutes, 40 seconds later)
20000s	(5 hours, 33 minutes, 20 seconds later)
24000s	(6 hours, 40 minutes later)
28000s	(7 hours, 46 minutes, 40 seconds later)
32000s	(8 hours, 53 minutes, 20 seconds later)
36000s	(10 hours and 0 minutes later)
40000s	(11 hours, 6 minutes, 40 seconds later)
44000s	(12 hours, 13 minutes, 20 seconds later)
48000s	(13 hours and 20 minutes later)
52000s	(14 hours, 26 minutes, 40 seconds later)
56000s	(15 hours, 33 minutes, 20 seconds later)
60000s
64000s
68000s
72000s
76000s
80000s
84000s
88000s
92000s
96000s
100000s
104000s
108000s
112000s
116000s
120000s
124000s
128000s
132000s
136000s
140000s
144000s
148000s
152000s
156000s
160000s
164000s
168000s
172000s
176000s
180000s
184000s
188000s
192000s
196000s
200000s
204000s
208000s
212000s
216000s
220000s
224000s
228000s
232000s
236000s
240000s
244000s
248000s
252000s
256000s
260000s
264000s
268000s
272000s
276000s
280000s
284000s
288000s
292000s
296000s
300000s
304000s
308000s
312000s
316000s
320000s
324000s
328000s
332000s
336000s
340000s
344000s
348000s
352000s
356000s
360000s
364000s
368000s
372000s
376000s
380000s
384000s
388000s
392000s
396000s
400000s
404000s
408000s
412000s
416000s
420000s
424000s
428000s	(4 days, 22 hours, 53 minutes, 20 seconds later)
432000s	(five days)
```

I don't think we need to make 112 attempts.??

## Change the value

```
(Check the setting values)
# postconf

(Check the setting values)
# postconf | grep maximal_queue_lifetime
maximal_queue_lifetime = 5d

(Rewrite the setting values)
# postconf -e 'maximal_queue_lifetime = 600s'

(Check the setting values)
# postconf | grep maximal_queue_lifetime
maximal_queue_lifetime = 600s
```

Other setting values are also changed accordingly.

```
queue_run_delay = 200s
minimal_backoff_time = 300s
maximal_backoff_time = 600s
maximal_queue_lifetime = 600s
bounce_queue_lifetime = 600s
```

## Restart postfix

Restart postfix, which can be done from Tools & Settings > Services in Plesk.

## Plesk Help Center article

<a href="https://support.plesk.com/hc/en-us/articles/213402609-How-to-change-the-mail-queue-lifetime-for-Postfix" target="_blank">https://support.plesk.com/hc/en-us/articles/213402609-How-to-change-the-mail-queue-lifetime-for-Postfix</a>

## afterwards

Operate with the following settings
```
queue_run_delay = 70s
minimal_backoff_time = 120s
maximal_backoff_time = 480s
maximal_queue_lifetime = 900s
bounce_queue_lifetime = 900s
```

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