I have dug through some of the forums and have yet to find the solution I'm looking for. I have a set of load balanced SMTP servers in my LTM with version 9.3.1 software installed. I have the SMTP health check enabled, however, it doesn't do exactly what I would like it to do. For example, I would like the F5, as part of the health check, to send an actual e-mail to the SMTP server and monitor the response to determine if the e-mail was successful or failed. I recently had an issue where /var on one of the systems filled up, and while the server was still responding to SMTP requests as one would expect, it was failing to accept any e-mails due to the drive being full. I would like the check to disable a node if it fails to receive an e-mail. If you could point me in the right direction, it would be greatly appreciated. Thank you in advance.

Interesting. So, you'd basically like the check to connect to the server, issue a helo, a mail from, an rcpt to, and if it sees "queued for delivery" or whatever, consider it up? Does your mail server have any sort of spam protection which would limit the amount of connections from a single IP?

You could potentially do this with a scripted monitor using expect. Or if that doesn't work, an external monitor calling a shell script should do it. Scripted MonitorExternal monitor template Aaron

@Chris. That's exactly what I'm trying to accomplish. While knowing port 25 is listening is nice and important, I need to also determine if the server is accepting mail. I'm looking to ensure I get a 250 response code essentially. @Hoolio: Thanks for the info. I'll look into this.

I think I can do this with the send/expect. However, how can I set a variable to be the IP of the node that is running the check. For instance, I have two SMTP servers in my LTM, I create the expect to be something like the following: send telnet 25 expect 220 send ehlo expect 250 send mail from: expect 250 send rcpt to: expect 250 send DATA expect 354 send Test send . expect 250 Essentially, I want my F5 to disable the node if it gets anything but a 250 or 354 at any point in this session.

whoops. It did some code cleaning. there should be ip_address between telnet and 25 as well as after ehlo. And email_address after from and to

Custom monitor for SMTP servers

11 Replies

Chris_Miller
Altostratus
Feb 08, 2011
Interesting. So, you'd basically like the check to connect to the server, issue a helo, a mail from, an rcpt to, and if it sees "queued for delivery" or whatever, consider it up? Does your mail server have any sort of spam protection which would limit the amount of connections from a single IP?
hooleylist
Cirrostratus
Feb 08, 2011
You could potentially do this with a scripted monitor using expect. Or if that doesn't work, an external monitor calling a shell script should do it.

Scripted Monitor
External monitor template

Aaron
dsirrine_23403
Nimbostratus
Feb 21, 2011
@Chris. That's exactly what I'm trying to accomplish. While knowing port 25 is listening is nice and important, I need to also determine if the server is accepting mail. I'm looking to ensure I get a 250 response code essentially.

@Hoolio: Thanks for the info. I'll look into this.
dsirrine_23403
Nimbostratus
Feb 23, 2011
I think I can do this with the send/expect. However, how can I set a variable to be the IP of the node that is running the check. For instance, I have two SMTP servers in my LTM, I create the expect to be something like the following:

send telnet 25

expect 220

send ehlo

expect 250

send mail from:

expect 250

send rcpt to:

expect 250

send DATA

expect 354

send Test

send .

expect 250

Essentially, I want my F5 to disable the node if it gets anything but a 250 or 354 at any point in this session.
dsirrine_23403
Nimbostratus
Feb 23, 2011
whoops. It did some code cleaning. there should be ip_address between telnet and 25 as well as after ehlo. And email_address after from and to
dsirrine_23403
Nimbostratus
Mar 09, 2011
I got it to work. I didn't need the initial "send telnet" as the scripted monitor does that to begin with. Unfortunately, I can't use pop/imap/etc as this is to test an exim gateway and can't necessarily "retrieve" the e-mail from the impacted system. doing an "ehlo" on localhost rounds it out nicely. Here's what I ended with:

expect 220 send "HELO localhost\r\n" expect "250" send "MAIL FROM: @localhost\r\n" expect "250" send "RCPT TO: @localhost\r\n" expect "250" send "DATA\r\n" expect "354" send "SUBJECT:F5 LTM SMTP Health Check\r\n" send "\r\n" send "This e-mail is generated by the SMTP health check by the F5 LTM.\r\n" send ".\r\n" expect "250" send "quit\r\n" expect "221"

where
= a local account that the mailbox has been redirected to /dev/null. If /var is full, I get an error of not being able to write to spooler, otherwise, I get a 250 OK.
hooleylist
Cirrostratus
May 27, 2011
Thanks for the solution dsirrine. I added it to the Codeshare here:

http://devcentral.f5.com/wiki/default.aspx/AdvDesignConfig/SMTP_scripted_monitor.html

Aaron
Techgeeeg
Nimbostratus
May 08, 2012
Hi,

This script was written for which MS Exchange2010 or earlier.... and is it expected to work with all the MS & TMOS platform or only the selected ones.

Regards,
hooleylist
Cirrostratus
Jul 31, 2012
Hi Techgeeg,

The scripted monitor should work with any SMTP server.

Aaron
Torsten_93742
Nimbostratus
Nov 26, 2014
Hi, the links in this post are outdated:

External monitor template: https://devcentral.f5.com/wiki/AdvDesignConfig.TemplateForExternalLtmMonitors.ashx

SMTP monitor at Codeshare: https://devcentral.f5.com/wiki/AdvDesignConfig.SMTP_scripted_monitor.ashx

Cheers, Torsten