Fastmail send to IMAP folder/label structure

I have been exploring Fastmail because I really appreciate well-designed software. I like the keyboard shortcuts and have always preferred a label system over a folder system as email truly can relate to more than one thing. One feature of which I just became aware is the ability to “automatically” file a message if it is sent to an email address such as this: label(or folder)@username.domain. So if I’m aware of the structure of the IMAP account, I can send an emal to waitingfor@myname.mydomain and it will be labeled waitingfor or filed in the waitingfor folder. Or I can BCC that same address to have the label added to my sent items.

My question is: what other system has this? I used this feature long ago, but I can’t remember what email provider or client provided this feature. Was it Gmail? Thanks for getting this off my mind.

I know Gmail allows “plus addressing” - but I’ve honestly never heard of what you’re talking about before.

But basically it (functionally) requires making Fastmail your DNS host, so if you’ve been using custom domains that may be a clue as to what other provider would have allowed it. It would’ve been one of your DNS providers. :slight_smile:

Go on to Fastmail’s web site for mail and look at what you can do with their server-based rule. More powerful than anything on your local machine…


Are you sure about that?

The label is not part of the domain, so I think DNS is not responsible for this?

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Yes, Gmail uses labels rather than folders. And, as @webwalrus mentioned you can use “plus addressing” ( to identify inbound mail.

I tried this in the past and and eventually gave up on the practice. Today I just use rules to sort inbound mail based on the address and/or domain name. For example I have one rule, that matches more than 25 addresses, (address1 OR address2 OR address3 . . . ) that says: Skip Inbox, Star it, Apply label “Notifications”. Another might say: Star it, Apply label “Broker”, Mark it as important.

When I receive a new message that I want to add to an existing rule I add the address followed by OR to the existing list of addresses.

Currently three rules handle 90% of my messages. The rest I delete, snooze, archive, or assign to a task as they are received. I can add or remove labels to messages whenever I choose.

Fastmail, Google Workspace, or . . . whichever service you choose I agree with @rms . Use server side rules to handle your inbound mail.

It gets through to Fastmail because I have a catch all address for the custom domain. Once it’s received by Fastmail, they (and not me as the user) apparently already set up a default rule to label a message if the first part of the address matches a label.

Fastmail supports both username+folder@domain and folder@username.domain. Either method will behave similar to Google’s “plus” method.

Yes. For subdomain addressing, DNS is involved - and Fastmail’s solution, from what I’ve read, is to be the DNS host. There’s no way around the DNS requirement.

For example: can be handled without it, because everything relevant is to the left of the @. It resolves the MX record for “”, and Fastmail can take it from there.

But for:

it’s sending email to user “amazon” at the third-level domain “”. For to receive mail it needs its own MX record. Theoretically you could set those up manually, but that’s exactly what you’d have to do - set up manual DNS entries for every subdomain.

Which is why Fastmail’s general solution seems to be to just let them host your DNS.

What are the pros and cons of letting Fastmail host your DNS?

I am not an expert on these issues, but Fastmail does not host my domain’s DNS and yet as a Fastmail customer I can handle the Plus Addressing and subdomain addressing. I just tested both and both works. Maybe a fluke, but I assume you that DNS is hosted elsewhere.

I think you can use wildcards in those MX records:

  • This is the easiest, most commonly used option for domain hosting with Fastmail.
  • Not recommended for users with a website at the domain hosted elsewhere.
  • We’ll automatically set up your domain so you can send and receive mail, sync contacts and calendars, and use the best security practices (DKIM, SPF, and more).
  • You will be able to manage your domain easily through your Fastmail settings. You can change your domain’s DNS records to let you set up a website or use other services hosted elsewhere.
  • We can spot common set up errors and will alert you to any problems.

Interesting. Curious as to what the MX record setup for that domain looks like, as what Rob found could very well be what you have set up.

Wildcard MX records are a weird critter, and probably not the sort of thing the average user would want to goof with. Hence, Fastmail offering to host your DNS.

I can’t think of any meaningful drawbacks whatsoever to doing that, as most drawbacks I can think of have to do with mail. :slight_smile: