# Running IMAPtest¶

imaptest is publicly available opensource IMAP/POP3/LMTP testing tool that has been developed by Dovecot.

Sample LMTP / POP3 configuration

  lmtp_port = 24
lmtp_max_parallel_count = 175
total_user_count = 500
rampup_time = 5

user aggressive {
count = 100%

mail_inbox_delivery_interval = 1s
mail_spam_delivery_interval = 0
mail_action_delay = 2s
mail_action_repeat_delay = 1s }

client pop3 {
count = 95%
connection_max_count = 1
protocol = pop3
pop3_keep_mails = no

client pop3 {
count = 5%
connection_max_count = 1
protocol = pop3
pop3_keep_mails = yes


## Key parameters:¶

lmtp_max_parallel_count = how many lmtp processes are allowed to run (should be about half of wanted lmtp deliveries per second) total_user_count = how many users we are using

• Related parameters from the user { … } * username_format =testuser_%03n@example.com * We will have total_user_count users padded to 3 numbers so if it’s 500 then we will have users: testuser_001@example.com to testuser_500@example.com

• username_start_index = the number of the first user * In example config we would be using testuser_501@example.com to testuser_1000@example.com

rampup_time = how many seconds to start generating the full load. This should be 5 to 10 seconds to distribute the load during the actual testing since it also affects the timing between connections for the users.

user aggressive { … } the name of the user profile, aggressive is just an example and if we have multiple users we want to have in the same profile it makes sense to have some descriptive name.

count = this is the percentage of users that should have this profile. If we only have one profile this should be set to 100 and if we have more they should add up to 100.

mail_inbox_delivery_interval = this is how often an user gets email delivered into the INBOX. In example configuration we have 500 users and just a single profile with this set to 1s so there should be approximately 500 deliveries happening per second.

mail_spam_delivery_interval = How often username+Spam should get email.

client pop3 { ... } we can specify multiple clients that are accessing the system.

count = the percentage of users that should behave according to client configuration. Should add up to 100 in total.

connection_max_count = how many connections should a single user have in parallel, for POP3 this should be 1

protocol = for pop3 this needs to be specified

pop3_keep_mails = yes/no, whether to keep mails in INBOX at the end of the session or delete everything

login_interval = how often should the user log in. For example if this is set to 1s and you have count = 100% and total_user_count = 500 you should have approximately 500 logins per second.

  lmtp_port = 24
lmtp_max_parallel_count = 175
total_user_count = 500
rampup_time = 5s

user aggressive {
count = 10%

mail_inbox_delivery_interval = 5s
mail_spam_delivery_interval = 0
mail_action_delay = 2s
mail_action_repeat_delay = 1s
mail_session_length = 3 min

mail_send_interval = 0
mail_write_duration = 0

mail_inbox_delete_percentage = 5
mail_inbox_move_percentage = 5
mail_inbox_move_filter_percentage = 10 }

user normal {
count = 90%

mail_inbox_delivery_interval = 120s
mail_spam_delivery_interval = 0
mail_action_delay = 3 min
mail_action_repeat_delay = 10s
mail_session_length = 20 min

mail_send_interval = 0
mail_write_duration = 0

mail_inbox_delete_percentage = 80
mail_inbox_move_percentage = 5
mail_inbox_move_filter_percentage = 10 }

client Thunderbird {
count = 80%
connection_max_count = 2
imap_idle = yes
imap_fetch_immediate = UID RFC822.SIZE FLAGS BODY.PEEK[HEADER.FIELDS (From To Cc Bcc Subject Date Message-ID Priority X-Priority References Newsgroups In-Reply-To Content-Type)]
imap_fetch_manual = RFC822.SIZE BODY[]
imap_status_interval = 5 min }

client AppleMail {
count = 20%
connection_max_count = 2
imap_idle = yes
imap_fetch_immediate = INTERNALDATE UID RFC822.SIZE FLAGS BODY.PEEK[HEADER.FIELDS (date subject from to cc message-id in-reply-to references x-priority x-uniform-type-identifier x-universally-unique-identifier)] MODSEQ
imap_fetch_manual = BODYSTRUCTURE BODY.PEEK[]
imap_status_interval = 5 min }


Most of the settings should be quite self explanatory or explained in the POP3/LMTP configuration.

## Running imaptest¶

First you need to make sure that you have high enough open file limit for the user running imaptest by doing something like: ulimit –n 65535 (this might also require editing nofile in /etc/security/limits.conf accordingly).

For very intense load testing it’s also possible to run out of TCP sockets so setting:sysctl –w net.ipv4.tcp_tw_reuse=1 helps.

imaptest pass=testpass host=127.0.0.1 mbox=testmbox profile=profile.conf clients=100 [no_pipelining]

• pass = all the users should have the same password

• host = host to connect to

• mbox = crlf terminated mbox format file to use for source emails (see generating mbox later in the document).

• profile = name of the appropriate profile.conf

• clients = how many concurrent clients

## optional:¶

• no_pipelining = for IMAP testing this can be specified to only send a single IMAP command at a time and waiting for a response before sending the next one. This should be used to get accurate IMAP latencies.

• secs = number of seconds to run the test, if this is not specified you need to end the process manually either with ctlr+c (if there are stuck connections and you want to force it to end, use ctrl+c twice) or killing it.

Example output:

Using the first POP3/LMTP configuration the output should be something like this:

\$ ./imaptest-370400225981/src/imaptest pass=testpass host=127.0.0.1 mbox=testmbox profile=pop3-profile.conf clients=100 secs=20

Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo LMTP

99    0    0   99    0  191    0    0  191    0   99   99   0/  0 [99%]

Warning: LMTP: Reached 175 connections, throttling

107    0    0  107    0  261    0    0  254    0  107  276   0/  0
103    0    0  103    0  243    0    0  243    0  103  336   0/  0
103    0    0  103    0   78    0    0   78    0  103  348   0/  0
108    0    0  108    0    0    0    0    0    0  108  266   3/  3
1      0    0   1     0    0    0    0    0    0    1  261   0/  0
0      0    0   0     0    0    0    0    0    0    0  347   0/  0
99     0    0   99    0  911    0    0  911    0   91  191   8/  8
96     0    0   92    0  357    0    0  347    0   10  274  94/ 94
135    0    0  138    0  616    0    0  613    0  132  387  97/ 97
30     0    0   23    0   38    0    0    6    0   0  159 ms/cmd avg

Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo LMTP

68    0    0   69    0  319    0    0  332    0  165  269   0/100
100   0    0  100    0    1    0    0    1    0  100  350   0/  0
1     0    0    1    0    0    0    0    0    0    1  350   0/  0
91    0    0   86    0  662    0    0  662    0   68  185  91/ 91
8     0    0   13    0  217    0    0  217    0   31  375   0/  0
100   0    0   57    0    0    0    0    0    0    2  260 100/100
16    0    0   59    0  578    0    0  578    0  114  265   0/100
183   0    0  183    0  637    0    0  637    0  183  350   0/  0
101   0    0  101    0   54    0    0   54    0  101  350   0/  0
24    0    0   25    0   16    0    0    1    0    0  125 ms/cmd avg

Totals:

Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo LMTP
1519    0    0 1519    0 5125    0    0 5118    0 1519 5714


The warning can be ignored because we are intentionally throttling number of LMTP connections.

You will have a line of output every second that is showing the number of commands sent per command. Login, List, Status, Select, Fetch, Fetch2, Store, Delete, Expunge, Append, Logout and LMTP delivery (lines 3, 5-13)

Every 10 seconds you get the line that shows average duration per connection (line 14). This is the most important one to watch, if the ms/cmd starts increasing then this indicates an issue with the platform. If everything is operating normally it should remain approximately the same for all commands.

At the end (lines 27-29) it will output you the total number of operations performed.

## Generating sample mbox¶

You can use the following script to create a test mbox with specific mail size distribution.

You might want to adjust your size_distribution dictionary according to your needs. The following will create an mbox with 5 mails of 10kB, 80kB, 150kB and 250kB each in a randomized order. Imaptest will go through the mbox sequentially so the randomness has to be in the mbox file.

  #!/usr/bin/env python

import mailbox, random, string, os
from email.mime.text import MIMEText
from email.utils import formatdate

mbox_out = 'testmbox'
mbox_tmp = '/tmp/testmbox'

mbox = mailbox.mbox(mbox_tmp)

mailfrom = 'sender@example.com'
mailto = 'recipient@example.com'
subject = 'Testmsg of %s kB'

size_distribution = {}
size_distribution[10] = 5
size_distribution[80] = 5
size_distribution[150] = 5
size_distribution[250] = 5
#size_distribution[15000] = 0

def splitrow(string, linelen):
step = linelen
out = []
for i in range(0, len(string), linelen):
out.append(string[i:step])
step += linelen
return '\n'.join(out)

date = formatdate()
mails = []
for key, val in size_distribution.items():

for mail in range(0, val):
mails.append(key)

random.shuffle(mails)

for val in mails:
body = ''.join(random.choice(string.ascii_lowercase + string.ascii_uppercase + string.digits + " .-") for _ in range(0, val*1024))
body = splitrow(body, 76)
msg = MIMEText(body + '\n')
msg.set_unixfrom('From %s %s' % (mailfrom, date))
msg['Date'] = date
msg['Subject'] = subject % val
msg['To'] = mailto
msg['From'] = mailfrom
msg['Message-ID'] = '<' + ''.join(random.choice(string.ascii_lowercase + string.ascii_uppercase + string.digits) for _ in range(0, 24)) + '>'
print 'Creating message of size {0} KB'.format(val)