Raspberri Pi email notifications setup with SendGrid

Came across a stupid problem: my scraper raspberry is getting full.

Instead of hooking the db file to the hard drive, I first wanted to fix a more generic issue: send notifications from my raspberry. What a rabbit hole.

Sendgrid lets you send 100 emails per day, that should do it. Registered.

Created an API key, then authenticated my domain under Settings/Sender Authentication. -> this is essential for sending emails - I had to create CNAME and TXT records as Sendgrid instructed me to do. I will refer to your domain you set here as YOUR.DOMAIN

Then log into your rPi and install postfix (steps in their docs)

sudo apt install postfix libsasl2-modules mailutils -y

On the configuration screen, select the second, "Internet Site" option: org/30-39 work, profession/35 linux, opsys, backup/assets/zJuFrgI.png

Edit /etc/postfix/main.cf If it's empty or does not exists, maybe you accidentally selected No Configuration.

Append the file with this:

smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_sasl_tls_security_options = noanonymous
smtp_tls_security_level = encrypt
header_size_limit = 4096000
relayhost = [smtp.sendgrid.net]:587

Then edit /etc/postfix/sasl_passwd Add

[smtp.sendgrid.net]:587 apikey:yourSendGridApiKey

to it, then

sudo chmod 600 /etc/postfix/sasl_passwd
sudo postmap /etc/postfix/sasl_passwd

To set your FROM address, create the file sudo nano /etc/mailutils.conf and add this as the content:

address {
  email-domain YOUR.DOMAIN;
};

By default, it'd use your hostname, that's rejected by sendgrid (stackoverflow info).

Finally restart your service:

sudo systemctl restart postfix

Test

echo "This is the mail body" | mail -s "new-subject" "user@mailinator.com"

You can also set the from field via the command line:

echo "Email Body" | mail -s "subject" -r "any-address-within@YOUR.DOMAIN" "user@mailinator.com"

I currently set an alarm for my pi to notify me if the memory card fills up with a simple crontab bash script, that sends a reminder every day (chatGPT generated)

#!/bin/bash

# Notify the user over this percentage:
threshold=70

# Where the email comes from: I name my Pis differently every time, so the hostname identifies which pi is having problems
FROM="$HOSTNAME.YOUR.DOMAIN"

# Flag file to track if notification has been sent today
flag_file="/tmp/memory_card_notification_sent"

# Check if flag file exists and if it's older than one day
if [ -f "$flag_file" ]; then
    # Get the modification time of the flag file in seconds since the epoch
    mod_time=$(date -r "$flag_file" +%s)

    # Get the current time in seconds since the epoch
    current_time=$(date +%s)

    # Calculate the difference in seconds between current time and modification time
    time_diff=$((current_time - mod_time))

    # If the flag file is older than one day (86400 seconds), remove it
    if [ "$time_diff" -gt 86400 ]; then
        rm "$flag_file"
    fi
fi

# Check if notification has been sent today
if [ -f "$flag_file" ]; then
    # Notification has already been sent today, exit script
    exit 0
fi

# Get the disk usage percentage
usage=$(df -h "/" | awk 'NR==2 {print $5}' | sed 's/%//')
# Check if disk usage exceeds the threshold
if [ "$usage" -ge "$threshold" ]; then
    # Send an email notification
    echo "Warning: Memory card is $usage% full." | mail -r $FROM -s "Memory card usage alert" "symunona+status@gmail.com"

    # Create flag file to indicate notification has been sent today
    touch "$flag_file"
fi
raspberry mail