h202-wq
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package mailbox
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import (
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"encoding/json"
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"fmt"
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"io"
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"log"
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"regexp"
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"strings"
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"time"
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"github.com/emersion/go-message"
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_ "github.com/emersion/go-message/charset"
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"github.com/knadh/go-pop3"
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"source.offmarket.win/aleagle/eaglecast/models"
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)
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// POP represents a POP mailbox.
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type POP struct {
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opt Opt
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client *pop3.Client
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lo *log.Logger
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}
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type bounceHeaders struct {
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Header string
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Regexp *regexp.Regexp
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}
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type bounceMeta struct {
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From string `json:"from"`
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Subject string `json:"subject"`
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MessageID string `json:"message_id"`
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DeliveredTo string `json:"delivered_to"`
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Received []string `json:"received"`
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ClassifyReason string `json:"classify_reason"`
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}
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var (
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// List of header to look for in the e-mail body, regexp to fall back to if the header is empty.
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headerLookups = []bounceHeaders{
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{models.EmailHeaderCampaignUUID, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderCampaignUUID + `:\s+?)([a-z0-9\-]{36})`)},
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{models.EmailHeaderSubscriberUUID, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderSubscriberUUID + `:\s+?)([a-z0-9\-]{36})`)},
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{models.EmailHeaderDate, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderDate + `:\s+?)([\w,\,\ ,:,+,-]*(?:\(?:\w*\))?)`)},
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{models.EmailHeaderFrom, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderFrom + `:\s+?)(.*)`)},
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{models.EmailHeaderSubject, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderSubject + `:\s+?)(.*)`)},
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{models.EmailHeaderMessageId, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderMessageId + `:\s+?)(.*)`)},
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{models.EmailHeaderDeliveredTo, regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderDeliveredTo + `:\s+?)(.*)`)},
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}
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reHdrReceived = regexp.MustCompile(`(?m)(?:^` + models.EmailHeaderReceived + `:\s+?)(.*)`)
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// SMTP status code (5.x.x or 4.x.x) to classify hard/soft bounces.
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reSMTPStatus = regexp.MustCompile(`(?m)(?i)^(?:Status:\s*)?(?:\d{3}\s+)?([45]\.\d+\.\d+)`)
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// List of (conventional) strings to guess hard bounces.
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reHardBounce = regexp.MustCompile(`(?i)(NXDOMAIN|user unknown|address not found|mailbox not found|address.*reject|does not exist|` +
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`invalid recipient|no such user|recipient.*invalid|undeliverable|permanent.*failure|permanent.*error|` +
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`bad.*address|unknown.*user|account.*disabled|address.*disabled)`)
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)
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// NewPOP returns a new instance of the POP mailbox client.
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func NewPOP(opt Opt, lo *log.Logger) *POP {
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return &POP{
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opt: opt,
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client: pop3.New(pop3.Opt{
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Host: opt.Host,
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Port: opt.Port,
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TLSEnabled: opt.TLSEnabled,
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TLSSkipVerify: opt.TLSSkipVerify,
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}),
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lo: lo,
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}
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}
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// Scan scans the mailbox and pushes the downloaded messages into the given channel.
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// The messages that are downloaded are deleted from the server. If limit > 0,
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// all messages on the server are downloaded and deleted.
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func (p *POP) Scan(limit int, ch chan models.Bounce) error {
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c, err := p.client.NewConn()
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if err != nil {
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return err
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}
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defer c.Quit()
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// Authenticate.
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if p.opt.AuthProtocol != "none" {
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if err := c.Auth(p.opt.Username, p.opt.Password); err != nil {
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return err
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}
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}
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// Get the total number of messages on the server.
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count, _, err := c.Stat()
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if err != nil {
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return err
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}
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// No messages.
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if count == 0 {
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return nil
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}
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if limit > 0 && count > limit {
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count = limit
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}
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// Download messages.
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for id := 1; id <= count; id++ {
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// Retrieve the raw bytes of the message.
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b, err := c.RetrRaw(id)
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if err != nil {
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p.lo.Printf("error retrieving bounce message %d: %v", id, err)
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continue
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}
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// Parse the message.
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m, err := message.Read(b)
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if err != nil {
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p.lo.Printf("error parsing bounce message %d: %v", id, err)
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continue
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}
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h := m
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// If this is a multipart message, find the last part.
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if mr := m.MultipartReader(); mr != nil {
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for {
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part, err := mr.NextPart()
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if err == io.EOF {
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break
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} else if err != nil {
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p.lo.Printf("error reading multipart bounce message %d: %v", id, err)
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continue
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}
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h = part
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}
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}
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// Reset the "unread portion" pointer of the message buffer.
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// If you don't do this, you can't read the entire body because the pointer will not point to the beginning.
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b, _ = c.RetrRaw(id)
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// Lookup headers in the e-mail. If a header isn't found, fall back to regexp lookups.
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hdr := make(map[string]string, 7)
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for _, l := range headerLookups {
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v := h.Header.Get(l.Header)
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// Not in the header. Try regexp.
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if v == "" {
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if m := l.Regexp.FindAllSubmatch(b.Bytes(), -1); m != nil {
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v = string(m[len(m)-1][1])
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}
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}
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hdr[l.Header] = strings.TrimSpace(v)
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}
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// Received is a []string header.
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msgReceived := h.Header.Map()[models.EmailHeaderReceived]
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if len(msgReceived) == 0 {
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if u := reHdrReceived.FindAllSubmatch(b.Bytes(), -1); u != nil {
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for i := range u {
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msgReceived = append(msgReceived, string(u[i][1]))
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}
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}
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}
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date, _ := time.Parse("Mon, 02 Jan 2006 15:04:05 -0700", hdr[models.EmailHeaderDate])
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if date.IsZero() {
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date = time.Now()
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}
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// Classify the bounce type based on message content.
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bounceType, bounceReason := classifyBounce(b.Bytes())
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// Additional bounce e-mail metadata.
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meta, _ := json.Marshal(bounceMeta{
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From: hdr[models.EmailHeaderFrom],
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Subject: hdr[models.EmailHeaderSubject],
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MessageID: hdr[models.EmailHeaderMessageId],
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DeliveredTo: hdr[models.EmailHeaderDeliveredTo],
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Received: msgReceived,
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ClassifyReason: bounceReason,
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})
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select {
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case ch <- models.Bounce{
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Type: bounceType,
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CampaignUUID: hdr[models.EmailHeaderCampaignUUID],
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SubscriberUUID: hdr[models.EmailHeaderSubscriberUUID],
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Source: p.opt.Host,
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CreatedAt: date,
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Meta: meta,
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}:
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default:
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}
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}
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// Delete the downloaded messages.
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for id := 1; id <= count; id++ {
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if err := c.Dele(id); err != nil {
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return err
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}
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}
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return nil
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}
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// classifyBounce analyzes the bounce message content and determines if it's a hard or soft bounce.
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// It checks SMTP status codes, diagnostic headers, and bounce keywords (using string heuristics).
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// soft is the default preference.
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// Returns the bounce type and a classification reason containing context about what matched.
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func classifyBounce(b []byte) (string, string) {
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if matches := reSMTPStatus.FindAllSubmatch(b, -1); matches != nil {
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for _, m := range matches {
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if len(m) >= 2 && len(m[0]) > 1 {
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// Full status code (e.g., "5.1.1").
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status := m[1]
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// 5.x.x is hard bounce.
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if status[0] == '5' {
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return models.BounceTypeHard, fmt.Sprintf("smtp_status=%s", status)
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}
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// 4.x.x is soft bounce.
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if status[0] == '4' {
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return models.BounceTypeSoft, fmt.Sprintf("smtp_status=%s", status)
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}
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}
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}
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}
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// Check for explicit hard bounce keywords.
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if match := reHardBounce.FindSubmatch(b); match != nil {
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return models.BounceTypeHard, fmt.Sprintf("body_match=%s", match[1])
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}
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return models.BounceTypeSoft, "default"
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}
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