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adding Enable/DisableMXCheck() option #188

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adding Enable/DisableMXCheck() option #188

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96d4ccf
adding Enable/DisableMXCheck() option
dcepler Jun 8, 2026
fee1dc6
correcting test
dcepler Jun 8, 2026
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6 changes: 6 additions & 0 deletions mx.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,12 @@ type Mx struct {

// CheckMX will return the DNS MX records for the given domain name sorted by preference.
func (v *Verifier) CheckMX(domain string) (*Mx, error) {
if !v.mxCheckEnabled {
return &Mx{
HasMXRecord: false,
}, nil
}

domain = domainToASCII(domain)
mx, err := net.LookupMX(domain)
if err != nil && len(mx) == 0 {
Expand Down
15 changes: 15 additions & 0 deletions verifier.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ import (

// Verifier is an email verifier. Create one by calling NewVerifier
type Verifier struct {
mxCheckEnabled bool // MX record check enabled or disabled (enabled by default)
smtpCheckEnabled bool // SMTP check enabled or disabled (disabled by default)
catchAllCheckEnabled bool // SMTP catchAll check enabled or disabled (enabled by default)
domainSuggestEnabled bool // whether suggest a most similar correct domain or not (disabled by default)
Expand Down Expand Up @@ -50,6 +51,7 @@ func init() {
// NewVerifier creates a new email verifier
func NewVerifier() *Verifier {
return &Verifier{
mxCheckEnabled: true,
fromEmail: defaultFromEmail,
helloName: defaultHelloName,
catchAllCheckEnabled: true,
Expand Down Expand Up @@ -167,6 +169,19 @@ func (v *Verifier) DisableSMTPCheck() *Verifier {
return v
}

// EnableMXCheck enables MX record check by dns,
// we check MX record by default
func (v *Verifier) EnableMXCheck() *Verifier {
v.mxCheckEnabled = true
return v
}

// DisableMXCheck disables MX record check by dns

@NeoCN NeoCN Aug 13, 2026

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Worth documenting the scope here: this flag can't skip the MX lookup when the SMTP check is
on. newSMTPClient does its own net.LookupMX and needs the result to know where to
connect, with no A-record fallback:

email-verifier/smtp.go

Lines 116 to 124 in fee1dc6

func newSMTPClient(domain, proxyURI string, connectTimeout, operationTimeout time.Duration) (*smtp.Client, *net.MX, error) {
domain = domainToASCII(domain)
mxRecords, err := net.LookupMX(domain)
if err != nil {
return nil, nil, err
}
if len(mxRecords) == 0 {
return nil, nil, errors.New("No MX records found")

So DisableMXCheck().EnableSMTPCheck() still pays for the DNS round trip, and reports
has_mx_records: false next to a possibly-true smtp.host_exists. That's inherent rather
than fixable, but saying so here would save the next reader a trip through smtp.go:

Suggested change
// DisableMXCheck disables MX record check by dns
// DisableMXCheck disables the standalone MX record check performed by Verify.
// Note this does not prevent the MX lookup inside the SMTP check, which needs
// MX records to locate a mail server.

func (v *Verifier) DisableMXCheck() *Verifier {
v.mxCheckEnabled = false
return v
}

// EnableCatchAllCheck enables catchAll check by smtp
// for most ISPs block outgoing catchAll requests through port 25, to prevent spam,
// we don't check catchAll by default
Expand Down
29 changes: 29 additions & 0 deletions verifier_test.go
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Expand Up @@ -250,6 +250,35 @@ func TestCheckEmail_DisabledSMTPCheck(t *testing.T) {
assert.Equal(t, &expected, ret)
}

func TestCheckEmail_DisabledMXCheck(t *testing.T) {
var (
// trueVal = true
username = "email_username"
domain = "randomain.com"
address = username + "@" + domain
email = address
)

verifier := NewVerifier().DisableMXCheck()
ret, err := verifier.Verify(email)
expected := Result{
Email: email,
Syntax: Syntax{
Username: username,
Domain: domain,
Valid: true,
},
HasMxRecords: false,
Disposable: false,
RoleAccount: false,
Reachable: reachableUnknown,
Free: false,
SMTP: nil,
}
assert.NoError(t, err)
assert.Equal(t, &expected, ret)
}

func TestNewVerifierOK_AutoUpdateDisposable(t *testing.T) {
verifier.EnableAutoUpdateDisposable()
}
Expand Down