RFC states the formal rules for email addresses. However, in the real world ESPs accept addresses that are not RFC-valid, and reject addresses that are.
When we built our validator, we did so based on real-world data + RFC spec to ensure more accurate validation.
Custom Grammar Checks
Custom Mailbox Provider Grammar
All major mailbox providers have their own custom grammar rules that impact whether an email address is valid in the real world.
We’ve integrated custom grammar checks for Gmail, Hotmail, and Yahoo into our email validator and are always adding more custom grammar checks as we discover these rules.
firstname.lastname@example.org Doesn’t meet Gmail’s local parts rules.
email@example.com doesn’t meet Gmail’s local parts rules.
michael….is….firstname.lastname@example.org Meets local parts rules because dots are ignored.
michael….is….email@example.com meets local parts rules because dots are ignored.
Protect Your List From Typos
“Did you mean yahoo.com?”
People make typos all the time. Yahoo.com can easily become yaho.com and when it does, you can miss out on connecting with that customer.
That’s why we built in a suggestion service into our email validation service. When we have a suggestion for a common typos, we’ll return it along with invalid status, so you can offer the suggestion to your user.
Avoid high-risk recipients
Avoid High Risk Addresses
Our email validation API is your first line of defense against high-risk recipients. When validating an email address, we check for role-based addresses or disposable email domains.