I want to subscribe a fax number to a (private) Google Group mailing list, so each message sent to the list will arrive on the fax machine. I have tried several email-to-fax services include MaxEmail and MetroFax. The problem is that these services all authorize senders not based on the From: address but on the Return-Path of the envelope. And, every service I've tried disallows either + or = characters in that address.

However, Google Groups uses a Return-Path: of the form [email protected] in order to track bounce addresses. Thus, I can't authorize that address for the email-to-fax service.

It seems like most transactional email services use + and = in their Return-Path: to be able to track bounces effectively. However, I can't find an email-to-fax service that accommodates this.

Things I've considered or tried:

  1. Finding an email-to-fax service that allows a Sender alias to include + and = characters (since they're both legal characters!).

  2. Forwarding to a Gmail account, which would then forward to the fax number. However, the Gmail Return-Path: includes the same invalid characters.

  3. Finding an "enterprise" email-to-fax service that would accept all email to [email protected] and fax it, no matter what the From: or Return-Path is set to. Know one?

  4. Using an email account with Procmail to rewrite the envelope header. However, Dreamhost has discontinued their Procmail integration.

  5. Using Mandrill to rewrite the Return-Path:, but this seems to only rewrite the domain, which is not the problem.

Anyway, I can't believe this should be so hard, and I would greatly appreciate any suggestions.

Update: Just to put a name to it, the issue is that most mailing lists use a Variable Envelope Return Path, but I can't seem to find an email-to-fax service that supports the + and = characters that VERP uses.

3 Answers 3


I believe Ring Central Fax will do what you want.

I actually called them up to answer this question and here's the answers I got:

  1. While their site talks about attaching things to email and faxing them, they will fax the body of an email message (apparently as a / in lieu of a coversheet)
  2. The account has an address whitelist
  3. ... but the email addresses on that whitelist can apparently have pluses, equal signs and commas in with their letters. (I'm at a 92% confidence level in this information)
  4. ... to match the whitelist they said they check the From Header for whitelist matching. I'm only about 80% confident in this part of the answer, as the "senior tech rep" on call literally seemed to have no idea what RFC 821 was, or how you find such a thing on the Internet. I was really hoping he'd transfer me to someone who knew, but no dice.

But, I think this information is correct (after also fighting with them on fax header vs email message header, which was a fun bit of translation / telephone too)

Ring Central mostly advertises its VOIP capabilities and the fax stuff is kind of hard to find, so I'm hoping you missed this in your survey of email to fax solutions.


Google Docs and Sheets add-ons1 or Google Apps Script could help solve this issue.

Regarding add-ons, they could interact with the user Gmail mailbox, i.e., there is an add-on, Email Forwarder2, that allows to create rules to forward emails even of old messages and include options like "include headers" that could be helpful in this case.

Add-ons are built using Google Apps Script, so those users having programming skills could build a custom script like the one behind Email Forwarder.



The solution was to use Foiply and set up two different accounts, one for the VERP and one for the actual From address. Also, I needed to setup a Gmail account to do the forwarding, since it uses a constant VERP, while VERP from Google Groups changes with each message. Steps:

  1. Create a team account on foiply.com. You need to support two incoming addresses, not just one.
  2. Change one account to use the email address [email protected].
  3. Create a Gmail account that will be used for forwarding at [email protected]. This is necessary because forwarding from Gmail has a static VERP, while Google Group mailing list VERPs vary.
  4. In Gmail, set up forwarding to [email protected] (this number is a personal efax, for testing use a fax number you control). Later, you will replace this with the actual fax number.
  5. Receive a fax from Google with a confirmation code. Enter this code in Gmail setting to confirm forwarding.
  6. Contact foiply.com support and have them change sending email address to [email protected]. This is the VERP Google uses for forwarded mail from [email protected] to [email protected]. You can reach foiply via web chat and they say support will take 30 minutes to update. (This is because, by default, they don't let you enter an = character in the email address field.)
  7. Setup another foiply address to accept messages from [email protected] (for testing, it can accept messages from a personal email address you control).
  8. Add the email address to the [email protected] Google Group.
  9. Set up a filter to forward all mail sent to [email protected] to [email protected].
  10. Note that Foiply needs both the VERP address and the From address to be registered.
  11. Cross your fingers.

Obviously, it is insane that such a complex setup is necessary, but at least it works.

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