Technical Limitations and E2E PGP Encryption

Oct 13, 2025 by talynt.org 7 views

Why Reply-To Isn't Available in Webclient and Stripped from Bridge Sent Email: A Security No-Go Decision?

Understanding the Issue

As a user of ProtonMail, you may have encountered a frustrating limitation when trying to reply to emails sent from a mailing list or a bridge account. When you reply to an email from a collective@collective.org address, you cannot set a reply-to field to help the recipient respond to the original collective email address. This issue has been reported by users since 2015, and it's essential to understand the security concerns behind this limitation.

The Security Concerns

ProtonMail's decision to strip the reply-to field from bridge sent emails and not make it available in the webclient is rooted in security concerns. The primary issue is related to spam and trust. When you reply to an email, the reply-to field is used to determine the email address that the recipient's response should be sent to. However, if the reply-to field is not properly validated, it can be exploited by spammers to send emails that appear to come from a trusted source.

Spam and Trust-Related Concerns

One of the primary security concerns is that spammers can use the reply-to field to send emails that appear to come from a trusted source. For example, if a spammer sends an email to a collective@collective.org address and includes a reply-to field set to a malicious email address, the recipient may inadvertently respond to the spammer's email, thinking it's the original collective email address. This can lead to a loss of trust in the collective email address and potentially compromise the security of the collective members.

Technical Limitations and E2E PGP Encryption

Another security concern related to the reply-to field is the technical limitation of end-to-end (E2E) PGP encryption. When you send an email using E2E encryption, the email is encrypted on the sender's device and can only be decrypted by the intended recipient. However, if the reply-to field is not properly validated, it can be exploited by an attacker to send emails that appear to come from the original sender, but are actually encrypted with a different key.

Other Security Concerns

There are other security concerns related to the reply-to field that may not be immediately apparent. For example, if the reply-to field is not properly validated, it can be used to launch a phishing attack. A phishing attack is a type of social engineering attack where an attacker sends an email that appears to come from a trusted source, but is actually designed to trick the recipient into revealing sensitive information.

Conclusion

In conclusion, the decision to strip the reply-to field from bridge sent emails and not make it available in the webclient is rooted in security concerns related to spam and trust. While it may seem like a minor limitation, it's essential to understand the security implications of not properly validating the reply-to field. ProtonMail's decision to prioritize security over convenience is a testament to their commitment to protecting their users' data and preventing potential security breaches.

Recommendations

If you're a user of ProtonMail and you're experiencing issues with the reply-to field, there are a few recommendations you can follow:

Use a different email client or service that supports the reply-to field.
Use a different email address that is not associated with the collective email address.
Contact ProtonMail support to report the issue and request a feature update.

Future Development

While ProtonMail's decision to strip the reply-to field from bridge sent emails and not make it available in the webclient is rooted in security concerns, it's possible that future development may address this issue. If you're interested in seeing this feature implemented, you can submit a feature request to ProtonMail's user voice forum.

Additional Information

As a user of ProtonMail, you may have noticed that the collective@collective.org address is redirected to multiple email addresses, including internal-archive@collective.org, your personal Proton email, and the personal email of each other collective member. This redirection is likely used to ensure that emails sent to the collective address are received by multiple members of the collective. However, this redirection may also contribute to the security concerns related to the reply-to field.

Conclusion

In conclusion, the decision to strip the reply-to field from bridge sent emails and not make it available in the webclient is a security no-go decision that is rooted in concerns related to spam and trust. While it may seem like a minor limitation, it's essential to understand the security implications of not properly validating the reply-to field. ProtonMail's commitment to security is a testament to their dedication to protecting their users' data and preventing potential security breaches.
Q&A: Why Reply-To Isn't Available in Webclient and Stripped from Bridge Sent Email

Q: What is the main reason why ProtonMail doesn't allow reply-to in webclient and strips it from bridge sent emails?

A: The main reason is security concerns related to spam and trust. If the reply-to field is not properly validated, it can be exploited by spammers to send emails that appear to come from a trusted source.

Q: How can spammers exploit the reply-to field?

A: Spammers can use the reply-to field to send emails that appear to come from a trusted source. For example, if a spammer sends an email to a collective@collective.org address and includes a reply-to field set to a malicious email address, the recipient may inadvertently respond to the spammer's email, thinking it's the original collective email address.

Q: What is the technical limitation related to E2E PGP encryption that contributes to the security concerns?

A: When you send an email using E2E encryption, the email is encrypted on the sender's device and can only be decrypted by the intended recipient. However, if the reply-to field is not properly validated, it can be exploited by an attacker to send emails that appear to come from the original sender, but are actually encrypted with a different key.

Q: Are there other security concerns related to the reply-to field?

A: Yes, there are other security concerns related to the reply-to field that may not be immediately apparent. For example, if the reply-to field is not properly validated, it can be used to launch a phishing attack. A phishing attack is a type of social engineering attack where an attacker sends an email that appears to come from a trusted source, but is actually designed to trick the recipient into revealing sensitive information.

Q: Can I use a different email client or service that supports the reply-to field?

A: Yes, you can use a different email client or service that supports the reply-to field. However, keep in mind that this may not be a secure solution, as it may not provide the same level of security as ProtonMail.

Q: Can I contact ProtonMail support to report the issue and request a feature update?

A: Yes, you can contact ProtonMail support to report the issue and request a feature update. However, keep in mind that ProtonMail's decision to strip the reply-to field from bridge sent emails and not make it available in the webclient is rooted in security concerns, and it's possible that they may not implement this feature in the future.

Q: What is the future of the reply-to field in ProtonMail?

A: It's difficult to say what the future of the reply-to field in ProtonMail will be. However, if you're interested in seeing this feature implemented, you can submit a feature request to ProtonMail's user voice forum.

Q: Are there any workarounds for this issue?

A: Yes, there are a few workarounds for this issue. For example, you can use a different email address that is not associated with the collective email address, or you can use a different email client or service that supports the reply-to field.

Q: Why is the collective@collective.org address redirected to multiple email addresses?

A: The collective@collective.org address is likely redirected to multiple email addresses to ensure that emails sent to the collective address are received by multiple members of the collective. However, this redirection may also contribute to the security concerns related to the reply-to field.

Q: Can I use a different email address for the collective?

A: Yes, you can use a different email address for the collective. However, keep in mind that this may not be a secure solution, as it may not provide the same level of security as ProtonMail.

Q: What is the best way to handle this issue?

A: The best way to handle this issue is to use a different email client or service that supports the reply-to field, or to use a different email address that is not associated with the collective email address. You can also contact ProtonMail support to report the issue and request a feature update.