Bounce messages are sent back to CleverReach by the receiving servers should an email not be delivered. These messages vary even though in principal they all point out that an email could not be delivered. Here is an overview of the most common bounce messages:
Incorrect Address |
| host is unknown / host not found |
| invalid adress / invalid recipient |
| mailbox not found / mailbox is unavailable |
| no mailbox here by that time |
| no such user |
| recipient e-mail adress unknown |
| user unknown / unknown user |
| said: 550 |
Filtering by Receiving Server |
| mail was identified as spam |
| only registered users may use this system |
| recipient adress rejected |
| relay not permitted |
Hardware Issues on Receiving Server |
| error writing message |
| message could not be stored |
| relay access denied |
Mailbox Issues |
| mailbox does not exist |
| mailbox has been deactivated / disabled / discontinued |
| mailbox is full |
| mailbox unavaliable |
| user has exhausted allowed storage space |
The messages said: 550 and said: 553 are used by some servers to classify bounced emails as spam. Basically every server can send custom bounce messages and there is no ONE standard. The overview above represents the most common bounce messages known to us.
We recommend reading the linked page to optimize deliverability of your emails.
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