Email Address Validation

The validate command checks if email addresses are likely deliverable before you send emails. This helps prevent bounce-backs and improves email deliverability.

Overview

Email validation performs several checks to determine if an email address can receive messages:

Syntax validation - Checks if the email format is valid (RFC 5322 compliant)
Domain validation - Verifies the domain exists via DNS lookup
MX record check - Confirms the domain has mail server records configured
SMTP verification (optional) - Attempts to verify with the mail server directly

Basic Usage

bash

# Validate a single email address
mailos validate [email protected]

# Validate multiple email addresses
mailos validate [email protected] [email protected] [email protected]

# Using the --email flag (can be repeated)
mailos validate --email [email protected] --email [email protected]

Command-Line Flags

Basic Options

Flag	Short	Type	Default	Description	Example
`--email`	`-e`	[]string		Email address(es) to validate (can be repeated)	`mailos validate --email value`

Advanced Options

Flag	Short	Type	Default	Description	Example
`--full`		bool	false	Perform full validation including SMTP check (slower)	`mailos validate --full`
`--quick`		bool	false	Perform quick validation (syntax + MX only)	`mailos validate --quick`

Output Options

Flag	Short	Type	Default	Description	Example
`--json`		bool	false	Output results as JSON	`mailos validate --json`
`--verbose`	`-v`	bool	false	Show detailed validation information	`mailos validate --verbose`

Command Flags

Flag	Short	Type	Default	Description
`--email`	`-e`	string[]		Email address(es) to validate (can be repeated)
`--verbose`	`-v`	bool	false	Show detailed validation information
`--json`		bool	false	Output results as JSON
`--full`		bool	false	Perform full validation including SMTP check (slower)
`--quick`		bool	false	Perform quick validation (syntax + MX only)

Examples

Basic Validation

bash

$ mailos validate [email protected]

Email Address Validation Results
================================
Checked at: 2025-01-15 10:30:45

  [email protected]

--------------------------------
Summary: 1 valid, 0 invalid

Verbose Output

bash

$ mailos validate [email protected] [email protected] --verbose

Email Address Validation Results
================================
Checked at: 2025-01-15 10:30:45

  [email protected]
   Syntax: OK | Domain: OK | MX: OK
   Mail servers: in1-smtp.messagingengine.com, in2-smtp.messagingengine.com
   Details: Email address appears to be valid and deliverable

  [email protected] - Domain does not exist
   Syntax: OK | Domain: FAIL | MX: FAIL
   Details: The domain 'nonexistent-domain.xyz' could not be found. DNS lookup failed.

--------------------------------
Summary: 1 valid, 1 invalid

JSON Output

bash

$ mailos validate [email protected] --json

json

[
  {
    "email": "[email protected]",
    "is_valid": true,
    "syntax_valid": true,
    "domain_valid": true,
    "mx_valid": true,
    "deliverable": true,
    "details": "Email address appears to be valid and deliverable",
    "mx_records": ["gmail-smtp-in.l.google.com", "alt1.gmail-smtp-in.l.google.com"],
    "checked_at": "2025-01-15T10:30:45Z"
  }
]

Full SMTP Validation

For more thorough validation, use the --full flag which attempts to connect to the mail server:

bash

$ mailos validate [email protected] --full --verbose

Note: SMTP verification can be slow and may be blocked by some mail servers. Many servers reject verification attempts for security reasons, so a failed SMTP check doesn't necessarily mean the address is invalid.

Integration with Send Command

Email validation is automatically enabled when sending emails. The send command will validate all recipients before attempting to send.

bash

# Validation happens automatically (enabled by default)
mailos send --to [email protected] --subject "Hello" --body "Hi there"

# Skip validation if needed
mailos send --to [email protected] --subject "Hello" --body "Hi there" --no-validate

# Force send even if validation fails
mailos send --to [email protected] --subject "Hello" --body "Hi there" --force

# Enable SMTP verification during send
mailos send --to [email protected] --subject "Hello" --body "Hi there" --validate-smtp

Send Command Validation Flags

Flag	Type	Default	Description
`--validate`	bool	true	Validate recipient email addresses before sending
`--no-validate`	bool	false	Skip email address validation
`--validate-smtp`	bool	false	Perform SMTP verification during validation (slower)

Validation Results

Valid Email

When an email passes all checks:

Syntax is correct
Domain exists and resolves
MX records are configured
(Optional) SMTP server accepts the address

Invalid Email - Common Errors

Error	Description
`Invalid email syntax`	Email format doesn't match RFC 5322 standards
`Domain does not exist`	DNS lookup failed - domain may not exist or has expired
`No mail server found`	Domain has no MX records - cannot receive email
`Recipient rejected`	SMTP server explicitly rejected the address (full mode only)

Use Cases

Pre-Send Validation

Validate a list of recipients before a bulk send:

bash

# Validate all recipients first
mailos validate [email protected] [email protected] [email protected]

# If all valid, proceed with send
mailos send --to [email protected],[email protected],[email protected] --subject "Newsletter" --file newsletter.md

Scripting and Automation

Use JSON output and exit codes for automation:

bash

# Check exit code (0 = all valid, non-zero = some invalid)
if mailos validate [email protected] --json > /dev/null 2>&1; then
    echo "Email is valid"
else
    echo "Email is invalid"
fi

# Parse JSON output for detailed results
mailos validate [email protected] --json | jq '.[] | select(.deliverable == false)'

Cleaning Email Lists

Validate a list of emails and filter out invalid ones:

bash

# Read emails from file, validate, and output valid ones
cat emails.txt | xargs mailos validate --json | jq -r '.[] | select(.deliverable) | .email'

Performance Notes

Quick mode (--quick): Fastest, checks syntax and MX records only (~100ms per email)
Default mode: Balanced, includes domain DNS verification (~200-500ms per email)
Full mode (--full): Most thorough, includes SMTP verification (~1-5 seconds per email)

For bulk validation, consider using quick mode and only using full validation for critical addresses.

Limitations

SMTP verification is not definitive - Many mail servers block verification attempts or give false positives/negatives
Catch-all domains - Some domains accept all addresses even if the mailbox doesn't exist
Temporary failures - DNS or network issues can cause false negatives
Rate limiting - Validating too many emails quickly may trigger rate limits

send - Send emails with automatic validation
drafts - Create and manage email drafts
search - Search for emails

Email Address Validation ​

Overview ​

Basic Usage ​

Command-Line Flags ​

Basic Options ​

Advanced Options ​

Output Options ​

Command Flags ​

Examples ​

Basic Validation ​

Verbose Output ​

JSON Output ​

Full SMTP Validation ​

Integration with Send Command ​

Send Command Validation Flags ​

Validation Results ​

Valid Email ​

Invalid Email - Common Errors ​

Use Cases ​

Pre-Send Validation ​

Scripting and Automation ​

Cleaning Email Lists ​

Performance Notes ​

Limitations ​

Related Commands ​

Email Address Validation

Overview

Basic Usage

Command-Line Flags

Basic Options

Advanced Options

Output Options

Command Flags

Examples

Basic Validation

Verbose Output

JSON Output

Full SMTP Validation

Integration with Send Command

Send Command Validation Flags

Validation Results

Valid Email

Invalid Email - Common Errors

Use Cases

Pre-Send Validation

Scripting and Automation

Cleaning Email Lists

Performance Notes

Limitations

Related Commands