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PRTG SMTP&IMAP Roundtrip time suddenly got 4 times higher



Hello there,

we noticed that our PRTG SMTP&IMAP roundtrip time suddenly increased from about 3 seconds to 11 seconds several days ago - that came from one minute to the next. In the graph we see that it is the IMAP response time that increased that much while the SMTP response time stayed where it was before. This sensor sends a mail from one mail address to itself every minute.

  • We didn't change anything on the host machine PRTG runs on or on the mail server we monitor in this time.
  • We already tried to reboot the host machine PRTG runs on and also the mailserver we monitor with this probe. We also restarted the router the PRTG host machine is connected to. This didn't change anything.
  • We asked the datacenter engineers and they see the PRTG mail come in and confirmed that this mail is nearly instantly delivered to the INBOX. But it stays there nearly 10 seconds until PRTG fetches and deletes the mail.
  • We then set up a Thunderbird IMAP account and send an email manually from an external mail source to the monitored mail account. This mail is in the INBOX very quick and Thunderbird automatically shows it within a few seconds. Much faster than PRTG says with its 11 seconds IMAP response time.

So our question would be: Why does PRTG tell about 11 seconds roundtrip time while it's test mail in reality is in the INBOX very much faster and manual tests also show that mails are there much faster? In the last years PRTG always showed constantly its 3 seconds roundtrip time, and now suddenly it is 11 seconds.

btw: We monitor two other mailservers with the same IMAP/SMTP roundtrip sensor on the same PRTG installation and for these two sensors no change in the roundtrip time is to be found. So the machine/installation PRTG runs on can be ruled out to be responsible for the problem.

Greetings and thanks very much for any help, Matthias

prtg roundtrip smtp-imap

Created on Mar 28, 2023 2:47:02 PM

Last change on Mar 30, 2023 9:51:27 AM by  Felix Wiesneth [Paessler Support]

1 Reply



Hello Matthias,

Thanks for reaching out to us! I'd like to take a look into the log files of the (remote)- probe on which the roundtrip sensor got added.

We will require so called Probe Status Files. Please navigate to the Setup > System Administration > Administrative Tools page and scroll down to the Probe Administrative Tools > Write Probe Status Files > Go! button.

They are located at the Probe device where the problematic sensors are located and need to be sent manually (zip the folder "C:\ProgramData\Paessler\PRTG Network Monitor\Logs\debug". If you changed the default log file path and if the files have outdated time stamps, you can find the directory via the PRTG Administrator Tool ("http://www.paessler.com/manuals/prtg/prtg_server_administrator") below the "Logs and Info" tab.

You can send the files to [email protected] and refer to this KB article so that you do not need to describe it one more time.

Kind regards,
Felix Saure, Technical Support Team

Created on Mar 30, 2023 12:14:10 PM by  Felix Saure [Paessler Support]

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