基于Bash通过MX服务器批量验证邮箱地址的脚本需求

Got it, let's put together a script that does exactly what you need—no fancy tricks, just straightforward steps tailored for someone new to Bash. Here's a complete, commented script that walks through each part of your request:

#!/bin/bash

# Check if input file is provided
if [ $# -ne 1 ]; then
    echo "Usage: $0 <email-list.txt>"
    exit 1
fi

EMAIL_FILE="$1"
VALID_EMAILS="valid_emails.txt"
INVALID_EMAILS="invalid_emails.txt"

# Clear previous result files (uncomment the lines below if you want to append instead)
> "$VALID_EMAILS"
> "$INVALID_EMAILS"

# Loop through each line in the email file
while IFS= read -r email; do
    # Skip empty lines
    [[ -z "$email" ]] && continue

    # Check if email follows basic user@domain format
    if ! [[ "$email" =~ ^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$ ]]; then
        echo "$email" >> "$INVALID_EMAILS"
        echo "Skipping invalid format: $email"
        continue
    fi

    # Extract the domain part after @
    DOMAIN=$(echo "$email" | cut -d '@' -f 2)
    echo "Processing $email (domain: $DOMAIN)"

    # Get the highest-priority MX record for the domain
    # Using dig +short for clean output, sort by priority (lowest number = highest priority)
    MX_SERVER=$(dig +short mx "$DOMAIN" | sort -n | head -n 1 | awk '{print $2}')

    # Check if MX record exists for the domain
    if [[ -z "$MX_SERVER" ]]; then
        echo "$email" >> "$INVALID_EMAILS"
        echo "No MX record found for $DOMAIN"
        continue
    fi

    # Remove trailing dot from MX server address if present
    MX_SERVER=${MX_SERVER%.}

    # Use telnet to validate recipient via SMTP commands, timeout after 10s to avoid hanging
    SMTP_RESPONSE=$(timeout 10 telnet "$MX_SERVER" 25 << EOF
HELO localhost
MAIL FROM:<test@example.com>
RCPT TO:<$email>
QUIT
EOF
    )

    # Check if the RCPT TO command returned a success code (250 = accepted)
    if echo "$SMTP_RESPONSE" | grep -q "250.*OK"; then
        echo "$email" >> "$VALID_EMAILS"
        echo "$email is valid"
    else
        echo "$email" >> "$INVALID_EMAILS"
        echo "$email is invalid or server rejected verification"
    fi

done < "$EMAIL_FILE"

echo "Validation complete! Results saved to $VALID_EMAILS and $INVALID_EMAILS"

How This Script Works (Step-by-Step) #

• Input Check: First, it makes sure you provided an email list file. Run it like ./validate_emails.sh your_emails.txt.
• Result Files: It clears any existing valid_emails.txt and invalid_emails.txt (comment out the > "$VALID_EMAILS" lines if you want to append new results instead of overwriting old ones).
• Email Format Check: Uses a basic regex to skip emails that don't follow the standard user@domain structure.
• Domain Extraction: Pulls the domain part after @ using the cut command.
• MX Record Lookup: Uses dig to fetch MX records, sorts them by priority (lowest number = highest priority), and picks the top server to test.
• SMTP Validation: Connects to the MX server on port 25, sends basic SMTP commands, and checks if the server accepts the recipient address. The timeout command prevents the script from hanging if a server doesn't respond.
• Result Saving: Writes valid emails to valid_emails.txt and invalid ones (including bad format/no MX records) to invalid_emails.txt.

Notes for New Bash Users #

• Make the script executable first: Run chmod +x validate_emails.sh.
• You'll need these tools installed: dig (part of the dnsutils package), telnet, and timeout (usually pre-installed on most Linux systems).
• Some email servers block SMTP verification from unknown IPs or require a valid sender address—you can change test@example.com to a real email if needed, but most servers accept a generic one for verification.
• If you get "connection refused" errors, some MX servers might use port 587 instead of 25—just change the 25 in the telnet line to 587 and test.

内容的提问来源于stack exchange，提问作者Ateeb Khan