Frequency of Salesforce Mail Transfer Agent (MTA) email re-delivery

The following schedule shows the Salesforce MTA (Mail Transfer Agent) email re-delivery retry intervals. When the receiving mail server is unreachable, Salesforce retries delivery automatically over a 24-hour period. The retry intervals increase over time — this pattern is called exponential backoff, where each subsequent retry waits progressively longer before the next attempt. The intervals below are based on connectivity to the receiving mail server and the state of the Salesforce mail queue. Use these figures as a guide.

Salesforce Email Re-delivery Attempt Schedule

• Second Attempt — 5 minutes after the first attempt
• Third Attempt — 10 minutes after the second attempt
• Fourth Attempt — 20 minutes after the third attempt
• Fifth Attempt — 40 minutes after the fourth attempt
• Sixth Attempt — 1 hour and 20 minutes after the fifth attempt
• Seventh Attempt — 2 hours and 40 minutes after the sixth attempt
• Eighth Attempt — 5 hours and 20 minutes after the seventh attempt
• Ninth Attempt — 10 hours and 40 minutes after the eighth attempt

If the email cannot be delivered after 9 attempts over a 24-hour period, the delivery fails and no further re-delivery attempts are made. Salesforce does not send a failure notification by default — administrators should review email logs or configure bounce handling to monitor undeliverable emails.