What is a 421 email error?

421 – Your message was temporarily deferred by the recipient server. This is usually a result of too many connections in a short timeframe or too many messages.

How do I fix SMTP error 421?

How to Fix Error 421 Cannot Connect to SMTP Server?

  1. Send/Receive Groups window.
  2. Changing port numbers in Internet Email Settings window.
  3. Enabling “Use the same settings as my incoming mail server” option.
  4. Recreating Outlook account.
  5. Turning Off Firewall in Windows Settings.
  6. PST selection window in Stellar Repair for Outlook.

How do I fix Gmail SMTP error?

The second option is to enable ‘Less secure apps’ within GMAIL.

  1. Log into your GMAIL account.
  2. Navigate to the ‘Less secure apps’ page.
  3. Toggle to turn this feature ‘ON’.
  4. Wait at least 1 hour for Google to update this setting.
  5. Test your mail application again. It should now send correctly via SMTP.

What happens if SMTP server is down?

One of several outcomes are typical with SMTP servers and mail delivery: the mail can be lost and the sender will receive an error, or the sending mail servers will eventually retry message delivery (not all do), or the backup SMTP mail servers — if one or more of those is configured via DNS MX records — will do what …

What does an incoming mail server mean?

The mail has to sit somewhere before it gets delivered to you. The server that stores this mail and then sends it to your inbox is called an incoming mail server. It may also be referred to as a POP, POP3, or IMAP server.

Which protocol is used for communication among email servers?

Simple Mail Transfer Protocol (SMTP)
The Simple Mail Transfer Protocol (SMTP) is an internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages.