Google Apps Gmail - Delegated Account Not Included in Reply-To-All

I'm writing this post because I could not find any documentation on Google's support/help pages (this page will hopefully be updated at some point) and this took me way too long to figure out after originally thinking it was a bug (Google Support insists it is not a bug).

In our scenario, we have a shared account that we use for our accounting team. Each user has been added to the account using the Gmail Settings -> Accounts tab -> "Grant access to your account" option inside of the shared account. Users will log into their own account, click their name/avatar at the top right of Gmail, and then click the shared account to open the shared account in a new tab.

They also have the ability to send as the account using the Gmail Settings -> Accounts tab -> "Send mail as" option inside of the shared account.

We noticed that when users were replying to emails inside of the shared account, if one or more of the delegated accounts were in the TO or CC field they would not be included in the Reply-To-All. All other addresses would be added, but the delegated accounts were silently stripped out.

The fix is to do one of the following:

• Remove the user from Gmail Settings -> Accounts tab -> "Send mail as" inside of the shared account.
• Edit the Gmail Settings -> Accounts tab -> "Send mail as" option and uncheck "Treat as an Alias" inside of the shared account.