The answer is that the Cisco ESA silently drops the encrypted emails because the sender’s certificate is not trusted by the ESA. When the ESA’s policy is configured to decrypt incoming S/MIME messages for content scanning, it must validate the sender’s certificate against its trusted certificate store; if the certificate chain cannot be verified or the certificate is absent, decryption fails, and the policy’s failure action—often set to “drop” rather than “deliver undecryptable”—causes the message to be discarded without notification. On the Cisco SCOR 350-701 exam, this scenario tests your understanding of S/MIME decryption failure handling and the importance of certificate trust in email security policies. A common trap is assuming the issue is with the recipient’s certificate or key, when in fact the ESA must trust the sender’s signing certificate to perform decryption. Memory tip: “No trust, no decrypt, silent drop” — the ESA cannot scan what it cannot unlock.
350-701 Content Security Practice Question
This 350-701 practice question tests your understanding of content security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During an email security audit, it is discovered that encrypted emails sent between two partners are being silently dropped by the Cisco ESA. The ESA uses a policy that decrypts incoming S/MIME messages for scanning. What is the most likely cause of the dropped messages?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ESA cannot decrypt the messages because the sender's certificate is not trusted by the ESA.
The Cisco ESA decrypts incoming S/MIME messages to perform content scanning. If the sender's certificate is not trusted by the ESA (i.e., not in the ESA's trusted certificate store or the certificate chain cannot be validated), the ESA cannot decrypt the message. This causes the message to be silently dropped because the policy requires decryption for scanning, and failure to decrypt results in the message being discarded rather than delivered.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The ESA is configured to re-encrypt outbound messages that were decrypted.
Why it's wrong here
Re-encryption should work if decryption succeeds.
✓
The ESA cannot decrypt the messages because the sender's certificate is not trusted by the ESA.
Why this is correct
S/MIME decryption requires trusting the sender's certificate; otherwise, it may drop.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The messages contain encrypted attachments that exceed size limits.
Why it's wrong here
Size limits would cause a bounce, not silent drop.
✗
The ESA is using TLS to receive the messages and the partner's certificate is untrusted.
Why it's wrong here
TLS certificate issues affect delivery, not S/MIME decryption.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing transport-layer encryption (TLS) with message-level encryption (S/MIME), leading candidates to incorrectly select Option D, when the core issue is the ESA's inability to decrypt the S/MIME message due to an untrusted sender certificate.
Detailed technical explanation
How to think about this question
S/MIME uses a hybrid encryption scheme: the message is encrypted with a symmetric key, which is then encrypted with the recipient's public RSA key. The ESA must have the sender's certificate (or the CA that issued it) in its trusted store to validate the signature and extract the symmetric key for decryption. If the certificate is untrusted, the ESA cannot decrypt the symmetric key, and the message is dropped per the 'Decrypt for Scanning' policy action, which has no fallback to deliver the encrypted message.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-701 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Content Security — This question tests Content Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ESA cannot decrypt the messages because the sender's certificate is not trusted by the ESA. — The Cisco ESA decrypts incoming S/MIME messages to perform content scanning. If the sender's certificate is not trusted by the ESA (i.e., not in the ESA's trusted certificate store or the certificate chain cannot be validated), the ESA cannot decrypt the message. This causes the message to be silently dropped because the policy requires decryption for scanning, and failure to decrypt results in the message being discarded rather than delivered.
What should I do if I get this 350-701 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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