How do I check if an email address is valid before I send?

You can’t know with 100% certainty that an email address is deliverable until you actually send something and get a bounce back, but you can get pretty close before sending.

Practical ways to check an email address

1) Basic format check

Make sure it looks like:

• name@example.com

Rules to verify:

• has exactly one @
• has a domain after @
• no spaces
• domain contains at least one dot, like example.com

Example regex (simple, not perfect):

^[^\s@]+@[^\s@]+\.[^\s@]+$

2) Check the domain exists

Verify the domain part after @ actually has DNS records.
For example, for user@example.com, check whether example.com exists and has MX records.

• MX record = tells you which mail servers accept email for that domain.
• If there are no MX records, the domain may not accept email.

3) Use an email verification API

These services usually check:

• syntax
• domain/MX
• mailbox existence signals
• disposable email
• role accounts (info@, admin@)
• risk scoring

Examples:

• ZeroBounce
• NeverBounce
• Kickbox
• Hunter Email Verifier

4) Send a confirmation email

For the strongest real-world validation, send a confirmation link/code:

• “Click to confirm your email”
• Only proceed after the user clicks

This proves the recipient can access the mailbox.

5) Watch for bounce messages

If you send mail, monitor bounce-back responses:

• hard bounce = invalid address
• soft bounce = temporary issue

Important limitation

Some servers:

• block verification probes
• accept all addresses temporarily (“catch-all” domains)
• only reveal validity after delivery attempts

So pre-send checks are helpful, but not perfect.

Recommended approach

If you want a reliable workflow:

1. Check syntax
2. Check MX records
3. Use a verification API
4. Require confirmation email for critical actions

If you want, I can show you:

• a JavaScript/Python example for checking MX records, or
• a regex/email validation function for your app.