Proofpoint

4.1.1

Proofpoint could not verify the recipient and deferred delivery. Retry later. If it keeps failing, confirm the address with the recipient admin.

4.1.1-2

Proofpoint is still verifying this recipient address. Wait and retry. Do not treat it as a hard bounce yet.

5.1.1

Proofpoint says this user is unknown. Treat it as a hard bounce and remove the address.

5.1.1-2

Proofpoint quoted a downstream user-unknown reject from the final mail server. Treat it as a hard bounce and remove the address.

5.1.1-3

Proofpoint says this user is unknown. Treat it as a hard bounce and remove the address.

5.1.1-4

Proofpoint says this is not a valid email address. Verify spelling, then remove it if it stays wrong.

5.1.8

Proofpoint rejected the sender domain because it was not found. Make sure From and Return-Path domains exist and can receive mail.

5.1.8-2

Proofpoint says the sender domain does not exist. Make sure From and Return-Path domains exist and can receive mail.

5.5.2

Proofpoint needs a fully qualified sender address. Fix From and Return-Path to use real domains, then resend.

5.7.0

Proofpoint rejected this under the sender DMARC policy. Align SPF or DKIM with the From domain so DMARC passes, then resend.

5.7.1

Proofpoint marked this recipient address as invalid. Suppress it unless the recipient confirms a corrected address.

5.7.1-2

Proofpoint denied relaying. The recipient may not be a customer, or you are not allowed to use this relay. Send only to accepted recipients.

5.7.1-5

Proofpoint denied relay access. The recipient may not be a customer, or you are not allowed to use this relay.

5.7.1-3

Proofpoint blocked your IP on its dynamic reputation list. Request delisting, then retry after the block clears.

5.7.1-4

Proofpoint blocked your IP through Cloudmark Sender Intelligence. Request delisting, then retry after the block clears.

5.7.1

Proofpoint denied relay access. Send only to accepted recipients for that tenant.