fix: distinguish imap auth failures from transient errors with exponential backoff

app/jobs/inboxes/fetch_imap_email_inboxes_job.rb

@@ -15,6 +15,7 @@ class Inboxes::FetchImapEmailInboxesJob < ApplicationJob
     return false if inbox.account.suspended?
     return false unless inbox.channel.imap_enabled
     return false if inbox.channel.reauthorization_required?
+    return false if inbox.channel.in_backoff?
 
     return true unless ChatwootApp.chatwoot_cloud?
     return false if default_plan?(inbox.account)

app/jobs/inboxes/fetch_imap_emails_job.rb

@@ -17,11 +17,10 @@ class Inboxes::FetchImapEmailsJob < MutexApplicationJob
     key = format(::Redis::Alfred::EMAIL_MESSAGE_MUTEX, inbox_id: channel.inbox.id)
     with_lock(key, 5.minutes) { process_email_for_channel(channel, interval) }
     channel.clear_imap_backoff!
-  rescue *ExceptionList::IMAP_EXCEPTIONS => e
-    Rails.logger.error "Authorization error for email channel - #{channel.inbox.id} : #{e.message}"
-    channel.apply_imap_backoff!
-  rescue EOFError, OpenSSL::SSL::SSLError, Net::IMAP::BadResponseError, Net::IMAP::InvalidResponseError,
-         Net::IMAP::ResponseParseError, Net::IMAP::ResponseReadError, Net::IMAP::ResponseTooLargeError => e
+  rescue Imap::AuthenticationError => e
+    Rails.logger.error "Authentication error for email channel - #{channel.inbox.id} : #{e.message}"
+    channel.authorization_error!
+  rescue *ExceptionList::IMAP_TRANSIENT_EXCEPTIONS => e
     Rails.logger.error "Error for email channel - #{channel.inbox.id} : #{e.message}"
     channel.apply_imap_backoff!
   rescue LockAcquisitionError

app/services/imap/base_fetch_email_service.rb

@@ -107,7 +107,11 @@ class Imap::BaseFetchEmailService
 
   def build_imap_client
     imap = Net::IMAP.new(channel.imap_address, port: channel.imap_port, ssl: true)
-    imap.authenticate(authentication_type, channel.imap_login, imap_password)
+    begin
+      imap.authenticate(authentication_type, channel.imap_login, imap_password)
+    rescue Net::IMAP::NoResponseError => e
+      raise Imap::AuthenticationError, e.message
+    end
     imap.select('INBOX')
     imap
   end

lib/exception_list.rb

@@ -1,5 +1,7 @@
 require 'net/imap'
 
+class Imap::AuthenticationError < StandardError; end
+
 module ExceptionList
   REST_CLIENT_EXCEPTIONS = [RestClient::NotFound, RestClient::GatewayTimeout, RestClient::BadRequest,
                             RestClient::MethodNotAllowed, RestClient::Forbidden, RestClient::InternalServerError,
@@ -14,6 +16,12 @@ module ExceptionList
   IMAP_EXCEPTIONS = [
     Errno::ECONNREFUSED, Net::OpenTimeout,
     Errno::ECONNRESET, Errno::ENETUNREACH, Net::IMAP::ByeResponseError,
-    Net::IMAP::NoResponseError, SocketError
+    SocketError
   ].freeze
+
+  IMAP_TRANSIENT_EXCEPTIONS = (IMAP_EXCEPTIONS + [
+    EOFError, OpenSSL::SSL::SSLError, Net::IMAP::NoResponseError, Net::IMAP::BadResponseError,
+    Net::IMAP::InvalidResponseError, Net::IMAP::ResponseParseError,
+    Net::IMAP::ResponseReadError, Net::IMAP::ResponseTooLargeError
+  ]).freeze
 end