What If I've Reached the SMTP Limit on my Virtual Dedicated/Dedicated Server?

Category: Virtual Dedicated Linux
Keywords: SMTP Limit

There is a daily limit of 1,000 outbound emails from your dedicated/virtual dedicated server. There are several other reasons besides "standard email" that can cause you to reach this daily restriction. The following are a few things you can check:

Verify That Your Domain Name is Not Sending Out Bouncebacks.

The default Plesk setting is to bounce email sent to non-existent users. This means that if your domain is coolexample.com, and someone sends an email to a non-existent user (ex: johndoe@coolexample.com), it is defaulted to send a message back saying "This user does not exist". If your domain receives a lot of incoming mail to non-existent users, the daily limit can be hit in no time.

The solution is to modify your mail preferences to reject mail sent to non-existent users. To reject mail sent to non-existent users in Plesk:

From the Plesk control panel click Domains.
Click Select Domain, then click Mail.
Click Preferences and then click the Reject radio button, and click OK.

NOTE:You will need to do this for all domains on the server.

Test Your Server for an Open Relay.

Consult the Email Logs & Mail Utilities on Your Server.

Plesk/Linux Servers:
/usr/local/psa/var/log/maillog (Qmail log)
/var/qmail/bin/qmail-qstat (View the amount of messages currently in your outbound queue)
/var/qmail/bin/qmail-qread (List out all messages in your outbound queue)
find /var/qmail/queue -name XXXX | xargs cat | less (Read the entire contents of an email, including headers, where XXXX is the ~8 digit ID specified on the /var/qmail/bin/qmail-qread command)
cPanel:
/var/log/exim_mainlog
/var/log/exim_paniclog
/var/log/exim_rejectlog
/var/log/maillog exim -bpr | grep "<" | wc -l (View the amount of messages currently in your outbound queue)
exim -bp (List out all messages in your outbound queue)
cPanel also has a graphical mail queue layout that you can view inside WebHost Manager by going to Email > Mail Queue Manager.
Simple Control Panel:
/var/log/maillog (Postfix Log)
mailq (List out all messages in your outbound queue)
postcat -q $mailq_message_number | more (Read the contents of an email in your outbound queue)
Plesk Windows Servers:
All mail related messages are stored in text files on the server. To view messages in the outbound queue, browse to:
C:%Plesk Directory%PleskMail ServersMail EnableQueuesSMTPOutgoing
C:%Plesk Directory%PleskMail ServersMail EnableQueuesSMTPInbound (for incoming)
Right click on any of these files and open in Notepad.

Check Exim Mail Settings in cPanel

On cPanel servers, make sure you have :fail: instead of :blackhole: for your Exim mail settings. An article at http://www.configserver.com/free/fail.html details the differences between the two settings.

To set the default mail behavior to :fail:, you will want to execute the following command through SSH:

If your domains are set to :fail:, and your logs still show suspicious traffic that leads to continuous relay usage, then you most likely have problems with the Exim Callout system.

By default, exim.conf is set to use callouts to verify the existence of email senders. This means that every time an email is sent to your server from a new address, Exim connects to the relay server during the RCPT callout command. This places an entry into the Exim "mainlog" and uses a SMTP relay.

You can disable this feature by following these steps:

Log into WebHost Manager
Click on Exim Configuration Editor under the Service Configuration area of the left-hand toolbar.
In the second gray area titled Options you will see 4 checkboxes
Uncheck the third checkbox Use callouts to verify the existence of email senders
Click Save

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What If I've Reached the SMTP Limit on my Virtual Dedicated/Dedicated Server?