How To Fix Email Service Unavailable Delivery Issues with IPv6 on Amazon Linux

Author: erics, July 16th, 2021

PROBLEM: Email delivery to Google was failing with a “Service Unavailable” error:

relay=aspmx.l.google.com. [IPv6:2607:f8b0:400d:c0c::1a], dsn=5.0.0, stat=Service unavailable

1	relay=aspmx.l.google.com. [IPv6:2607:f8b0:400d:c0c::1a], dsn=5.0.0, stat=Service unavailable

Note that the network address for the destination is shown as IPv6! That is the root cause of the issue: 1. Sendmail is sending mail from the IPv6 address instead of the IPv4 address 2. Google rejects IPv6 senders without proper reverse […]

Categories: How-To's, Technology Tags: Amazon, Amazzon Linux, AWS, Delivery, DSN, Email, howto, IPv4, IPv6, Linux, make, Restart, SendMail, sendmail.cf, sendmail.mc, service, Service Unavailable, SPF, tips, Unavailable | No comments

How To List Running AWS Instances in all Regions Sorted by LaunchTime and Email in a Monospaced Font

Author: erics, July 1st, 2019

#!/bin/sh

DATE=`date`

(
echo "From: Your Full Name <you@yourdomain.com>"
echo "To: you@yourdomain.com"
echo "Subject: AWS Instances Report for All Customers as of $DATE"
cat <<EOT
MIME-Version: 1.0
Content-Type: text/html
Content-Disposition: inline
<html>
<body>
<pre style="font: monospace">
EOT
for profile in customer1 customer2 customer3; do
	for region in `aws ec2 describe-regions --output text | cut -f3`; do
		echo -e "\nListing Instances for profile $profile in region: '$region'..."
		aws ec2 describe-instances \
		--filters "Name=instance-state-name,Values=running" \
		--query 'Reservations[*].Instances[*].[InstanceId, PublicIpAddress, LaunchTime, InstanceType, Tags[?Key==`Name`] | [0].Value]| sort_by(@, &@[0][2])' \
		--region $region \
		--profile $profile \
		--output table
	done
done
cat <<EOT
</pre>
</body>
</html>
EOT
) | /usr/sbin/sendmail -t

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#!/bin/sh

DATE=`date`

(

echo "From: Your Full Name <you@yourdomain.com>"

echo "To: you@yourdomain.com"

echo "Subject: AWS Instances Report for All Customers as of $DATE"

cat <<EOT

MIME-Version: 1.0

Content-Type: text/html

Content-Disposition: inline

<html>

<body>

EOT

for profile in customer1 customer2 customer3; do

for region in `aws ec2 describe-regions --output text | cut -f3`; do

echo -e "\nListing Instances for profile $profile in region: '$region'..."

aws ec2 describe-instances \

--filters "Name=instance-state-name,Values=running" \

--query 'Reservations[*].Instances[*].[InstanceId, PublicIpAddress, LaunchTime, InstanceType, Tags[?Key==`Name`] | [0].Value]| sort_by(@, &@[0][2])' \

--region $region \

--profile $profile \

--output table

done

cat <<EOT

</pre>

</body>

</html>

EOT

) | /usr/sbin/sendmail -t

Categories: How-To's, Technology Tags: AWS, aws ec2, Date, EC2, Email, Font, Format, howto, html, LaunchTime, mail, monospace, monospaced, Multiple, Region, Regions, SendMail, sort, Sort By, time, tips | No comments

How To Force Sendmail to Process the Mail Queue

Author: erics, August 4th, 2016

To force sendmail to process the mail queue, execute as root: sendmail -q -v The optional -v enables verbose mode to assist with troubleshooting. To display the current contents of the mail queue, execute as root: mailq

Categories: How-To's, Technology Tags: Email, Force, howto, mail, Mail Queue, Mailq, Q, Queue, SendMail, tips | No comments

How To Enable Sendmail on CentOS 5

Author: erics, January 28th, 2011

# vim /etc/sysconfig/sendmail Change: DAEMON=no to DAEMON=yes

Categories: How-To's, Technology Tags: CentOS, howto, SendMail, tips | No comments

How To Setup A Smart Relay Host Port on Sendmail

Author: erics, January 26th, 2011

Configure the Smart Host Search for DS in /etc/mail/sendmail.cf and edit as follows: Before: DS After: DSyour.mail.relay.yourdomain.com Configure The Port Search for Mrelay and edit as follows: Before: Mrelay, P=[IPC], F=mDFMuXa8, S=EnvFromSMTP/HdrFromSMTP, R=MasqSMTP, E=\r\n, L=2040, T=DNS/RFC822/SMTP, A=TCP $h After: Mrelay, P=[IPC], F=mDFMuXa8, S=EnvFromSMTP/HdrFromSMTP, R=MasqSMTP, E=\r\n, L=2040, T=DNS/RFC822/SMTP, A=TCP $h 2525 Add the following line appropriately […]

Categories: How-To's, Technology Tags: DS, Email, Email Relay, howto, Port, Relay, SendMail, Smart Host, SmartHost, tips | No comments

How To Fix Email Service Unavailable Delivery Issues with IPv6 on Amazon Linux

How To List Running AWS Instances in all Regions Sorted by LaunchTime and Email in a Monospaced Font

How To Force Sendmail to Process the Mail Queue

How To Enable Sendmail on CentOS 5

How To Setup A Smart Relay Host Port on Sendmail

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