How Twilio SendGrid (TSG) Handles Auto Responses
When email recipients are out of the office for an extended period of time, they will often set an automatic response or "Out-of-Office" reply on their inbox. This sends an automated response to anyone sending a message to their inbox that they are not in the office and may also include if they are able to check mail during this time, when they will return, and who might be a point of contact in the interim.
TSG will not automatically handle these responses using the return-path which manages server replies such as bounces.
What is a Return-Path?
Return-path is a hidden email header that indicates where and how bounced emails will be processed. This header, also referred to as a bounce address or reverse path, is an SMTP address that is separate from your original sending address, and is used specifically for collecting and processing bounced messages.
This usually looks something like this in the received headers in an email sent through TSG:
How Automatic Replies are Sent
The designated 'reply-to' field of a sent email will be the email address used for human replies.
According to email RFC 3834 section 4, the return-path address of a sent message will be responsible for receiving automated "out-of-office" or other automated messages.
An "Out-of-Office" response relayed back through the TSG return-path associated with domain authentication does not result in any action nor is anything logged by TSG. Ultimately, neither TSG nor our customers are able to tell if an out of office reply was sent back.
Overwrite the Return-Path
You can ask that we not overwrite the return path so that auto responses come back to your 'from' address directly and as a result, we will not be able to track bounces and spam reports automatically. Essentially, we will no longer log bounces or spam reports to the account suppression lists and will subsequently not suppress future attempts to send to these recipients. If you ask that we not overwrite the return path, you will be responsible for removing hard bounces and spam reporting addresses from your contact lists to maintain a positive reputation.
How to Resolve
A request can be made with our support team to not overwrite the return-path for the account. This is an account-wide setting so it would impact all mail sent from a parent or sub user account.
- This will allow auto responses to return directly to the “From” address so that you will know if a recipient is out of the office and any details within the auto response.
- TSG will no longer be able to track bounces and spam reports automatically.
- TSG will no longer log bounces or spam reports to the account suppression lists and will subsequently be unable to suppress future attempts to send to these recipients. Repeated sending to these addresses can negatively impact your domain and IP reputation.
- The sender is responsible for removing hard bounces and spam reporting addresses from the contact lists to maintain a positive reputation.
- Recipient servers will check the information after the @ symbol for the domain authentication and check if it passes SPF. If we do not overwrite the return-path SPF, it will either return a "fail" or "neutral". The account holder will need to add an SPF record into their DNS with the type of TXT so that SPF will pass to improve deliverability.
If the return path that is not overwritten by TSG, it will appear as the from address which will receive any auto responses.
Disabling the overwriting of the return path is a way to ensure that you receive automatic replies, however, there are drawbacks. In particular, we will not handle information sent back through the return-path automatically. If the return path is not overwritten, TSG will no longer be responsible for handling server responses nor will we automatically suppress the associated email addresses. Instead, this will need to be managed by the TSG account holder.
- RFC (section 4): https://datatracker.ietf.org/doc/html/rfc3834#section-4
- Twilio SendGrid Blog (What is Return-Path) https://sendgrid.com/blog/what-is-return-path/
- Domain Authentication: https://sendgrid.com/docs/ui/account-and-settings/how-to-set-up-domain-authentication/