We use Office 365 Exchange Online for our emails. Whilst you can configure CiviCRM outbound mail to use it, you can't actually send mail using it. I have done some investigation, and the reason is that packages/Mail/smtp.php replaces the From address with the Return-Path. CiviCRM adds a VERP component, so Exchange Online rejects the email because the From address is invalid. Exchange overwrites the Return-Path with the From address anyway, so VERP doesn't work.

Any comments or thoughts? I assume someone will say that we should use another Mail Transport Agent.

  • 1
    You're right - use another MTA! CiviMail has always required an MTA that supports VERP, and Exchange is the only major MTA that doesn't. When I have clients using Exchange, I'll usually configure Postfix on their CiviCRM server to handle these mails. Jul 20, 2018 at 17:52
  • Thanks, we are using another MTA. I suppose Exchange is configured for human clients to send emails rather than systems. Jul 21, 2018 at 20:41
  • Related thoughts... I've got a CiviCRM install, where the client uses 365 Exchange Online. I'm using sendmail on the server to send and that seems to work just fine with a well set up SPF record. The only thing I haven't come to terms with is the bounce email address. I'm not sure how best to handle that. Jul 24, 2018 at 0:29
  • I have added some rules in Exchange to handle bounce messages, basically routing emails with the recipient starting with the local part to a given mailbox. You would still need to prevent the from address being the return-path. Jul 24, 2018 at 11:46

2 Answers 2


See the 'Support for Plus Addressing in Office 365' roadmap item for Exchange Online... due July 2020

"Plus Addressing is a great way to quickly create custom (or disposable) email addresses based off your standard email address, by simply adding a "+" suffix string to an existing email address in Office 365. For example, a plus address for [email protected] could be something like [email protected] that she could use to sign up for the newsletter at the Northwind web site. Then when Northwind sends a newsletter to [email protected] it will route directly to [email protected]. Kim could create an Inbox rule that then moves messages sent to this + address into the "Northwind" folder. Plus addressing support in Office 365 is a great way to more easily manage your Inbox, and even track mail like marketing and sales campaigns.

Featured ID: 59441 Added to Roadmap: 12/6/2019 Last Modified: 6/2/2020



ah, yes, Exchange. That mail server that behaves almost like the others, but not quite.

You have 3 paths out of that:

1) use a separate "normal" email server, eg postfix for sending your emails and set up a catch all email address on 365 to handle the bounces

2) use a mail provider for your mass mailing (sendgrid, mailjet, amazon aws...). They probably all need you to install a civicrm extension to handle the bounce events

3) contribute a feature to civicrm so it doesn't need VERP. This isn't that far away, the data of the VERP is already added as an extra line in the mail header and for what I've seen, most of the bounce emails copy it.

So the "only" things you'd need: prevent civi to rewrite the from email with a VERP and change the bounce processor to look at the extra header instead of the envelope email.

I'd suggest you 2, mostly because you are likely to have a better deliverability on your mass mailings than relying on exchange.

  • We've resorted to using our old email provider which can handle VERP messages. I suspect that Exchange doesn't like a VERP type return path. Various people have asked about this from time to time, but it seems our friends in Microsoft haven't responded. Jul 27, 2018 at 17:18
  • Which mail provider is that? Might be in the market...
    – jimcrist
    Jul 30, 2018 at 17:39

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