Summary
When looking at the Email Delivery Statuses report, you might see Soft Bounce or Hard Bounce in the status column.
Key Points
While there are many reasons an email address may soft bounce, below are some common reasons:
Mailbox is full (over quota)
Recipient email server is down or offline
Email message is too large
If an email address continues to soft bounce, the email will eventually be considered a hard bounce. We'll allow seven soft bounces for an email address with no previous activity and up to 15 soft bounces for recipients with previous email activity before converting a soft bounce into a hard bounce.
Once the hard-bounce occurs, it blocks future emails.
The most common reasons for a hard bounce is:
Name portion of the email address has a typo or the domain is of the wrong type (.net instead of .com, for example)
Email address is no longer valid
Email address is no longer in use
Server/recipient marked the email as Spam (this is more common than you think)
Recipient requested to unsubscribe through their email service