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Support for Dynamic '+' Email Aliases in Office 365


I am familiar with using a plus sign following my email alias to create dynamic unique addresses for a Gmail account. e.g. will arrive at my Gmail mailbox, where I can then apply rules based on the 'To:' address. See this page for details:

I tested this on my Office 365 address and it works, but only for email addresses in my parent domain. Using the aliases on subdomain addresses results in a 'recipient not found' NDR.

Does anyone out there have more information on this feature or if it even is one for 365 / Exchange?


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    Ryan Kendall shared this idea  ·   ·  Flag idea as inappropriate…  ·  Admin →


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      • Tim Phang commented  ·   ·  Flag as inappropriate

        As an exchange admin you can set this up for specific addresses. Follow the instructions in: and change the match rule in step 6 to be something along the lines of:


        This will catch "" and redirect it to the appropriate mailbox. This will need to be configured for each user who needs the functionality. For a team of developers to be able to use for testing, I'd recommend creating a shared inbox and applying the rule there.

      • Scott Carlow commented  ·   ·  Flag as inappropriate

        A bit late, but to the person who asked this:

        "The E-mail standard says that comments can be included by surrounding them in () at the beginning or end of the local part. Example:


        - or -


        Has anyone tried this with 365?"

        You are referencing RFC822, which was made obsolete be RFC2822. "Comments" are referring to things like the friendly name of a person or system name, and that syntax was replaced with addr-spec (e.g. [Comment or folding whitespace] "<"local@domain">". So in any case, this is not subaddressing, but addressing syntax.

        That said, It's mind boggling that implements this but not Office 365. While 365 accepts messages from addresses that use subaddressing and you can add subaddresses to mailboxes via Powershell and ECP, the implementation is quite poor especially when compared to their own *consumer* product. I am extremely surprised that Business and Enterprise clients even need to ask for this.

      • Kindle commented  ·   ·  Flag as inappropriate

        We once wanted to use Office 365 and startet with configuration, but then realised there's no support for + adressing. That's really bad, cause we couldn't use office365 then with all other benefits.

      • Josh commented  ·   ·  Flag as inappropriate

        We will sorely miss this feature now that we are with exchange. Please add this. Our development team has used this extensively and now we'll have to use an alternate email service to continue using it.

      • Andy Doyle commented  ·   ·  Flag as inappropriate

        Come on Microsoft... you already have this working for Hotmail/Outlook accounts and these sit on Office 365 now.

      • Anonymous commented  ·   ·  Flag as inappropriate

        It's really time this gets added. It's a great way to find out when a company has sold your email address.

      • John commented  ·   ·  Flag as inappropriate

        Do you know what makes this issue worse. Dynamic "+" addresses work on free Hotmail/Outlook addresses!

      • David commented  ·   ·  Flag as inappropriate

        Reported March 2017, no response as of July 2018? Nice. But I suppose it should be no surprise that Microsoft wouldn't follow the RFC's, nor listen to their users.

        I used to use this feature every day on G Suite and it looks like there's no chance of O365 getting this fairly basic functionality.

      • Dan commented  ·   ·  Flag as inappropriate

        My company's dev team could really use such a feature for testing our web application!

      • Scott Francis commented  ·   ·  Flag as inappropriate

        it's not just a genius idea, it's a REQUIREMENT from the relevant RFCs (822, 2822, etc.)

        Not supporting "+" in the user-part means an email handling software is in violation of the RFCs that specify the standards that must be adhered to.

      • [Deleted User] commented  ·   ·  Flag as inappropriate

        i am sorry but i does not work on Office 365 Business Premium accounts; even with the rule in the mail flow section. maybe I did something wrong.

      • Vinicius commented  ·   ·  Flag as inappropriate

        This workaround doesn't work in my environment. Throws the error:
        550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup

        I suppose it's checking the address existence before checking the mail flow role.

      • Anonymous commented  ·   ·  Flag as inappropriate


        Be able to receive emails to: "FirstPartOfYourMail+ANYTEXT@YourDomain"

        Here is how:
        - Got to Exchange admin portal
        - Go to MailFlow
        - Create a rule

        With the following settings:
        - Apply this rule:
        - "When recipient matches: "FirstPartOfYourMail+" <- please note the plus in the end
        - and :A recipients domain is "YourDomain"
        - Do the following
        - redirect messages to "ChooseYourExchangeMailbox" <= you will be able to select them from a list
        DO the following

        This will only ALLOW YOU TO receive Emails for disposable addresses though while google enabled you to also SEND emails from these addresses as they became a dynamic alias.

        That our MAIN concern was to loose emails as we were not able to receive emails from previously setup accounts anymore and it was impossible to run them all down. I hope somebody else that runs into this issue dosen't have to spend weeks to figure this out when the fix is relatively simple.

        Should somebody need to send from these emails you will have to add them one by one (this could also be scripted):
        - Add Alias for specific email that user wants to send with
        - Since the alias contains a "+" we CANNOT use the office admin portal as this wont let us enter "+" as alias, but we HAVE TO to use the Exchange admin portal
        - In Exchange admin portal go to Recipients
        - Double click on user you wanne add an alias for
        - go to email adress tab on user
        - now add the new alias (this interface allows us to enter a "+")
        - make sure you save after
        - done

      • Anonymous commented  ·   ·  Flag as inappropriate

        The E-mail standard says that comments can be included by surrounding them in () at the beginning or end of the local part. Example:


        - or -


        Has anyone tried this with 365?

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