How long does smtp keep trying to send mail

The amount of time SMTP (Simple Mail Transfer Protocol) keeps trying to send mail depends on various factors, including:

1. SMTP server configuration: The SMTP server's retry interval, maximum number of retries, and timeout values are set by the server administrator. These values can vary widely depending on the server and its purpose.
2. Mail client configuration: The mail client's (e.g., email client or application) retry interval, maximum number of retries, and timeout values are also set by the client administrator or user.
3. Network conditions: Network connectivity, latency, and packet loss can affect the SMTP server's ability to send mail. If the network is unreliable, the SMTP server may retry sending the mail multiple times before giving up.

Typically, an SMTP server will follow a retry strategy like this:

1. Initial attempt: The SMTP server sends the mail immediately.
2. First retry: If the initial attempt fails, the SMTP server will retry sending the mail after a short delay (e.g., 1-5 minutes).
3. Subsequent retries: If subsequent attempts fail, the SMTP server will retry sending the mail at increasingly longer intervals (e.g., 15-30 minutes, 1-2 hours, etc.).
4. Maximum retries: The SMTP server will eventually give up trying to send the mail if it exceeds a maximum number of retries (e.g., 5-10 attempts).

Here are some general guidelines on the retry intervals and maximum retries for popular SMTP servers:

• Postfix (a popular open-source SMTP server): 1 minute for the first retry, 5 minutes for the second retry, and 15 minutes for subsequent retries. The maximum number of retries is 5.
• Exim (another popular open-source SMTP server): 1 minute for the first retry, 5 minutes for the second retry, and 30 minutes for subsequent retries. The maximum number of retries is 5.
• Microsoft Exchange: The retry interval and maximum number of retries depend on the Exchange server configuration. Typically, Exchange will retry sending mail every 5-15 minutes, with a maximum of 5-10 attempts.

Keep in mind that these are general guidelines, and the actual retry strategy may vary depending on the specific SMTP server and its configuration.