How do you write an email with a prefilled subject?
Choose the email record type and enter the recipient, a subject and optionally a body. Tapping the tag opens a new message with those fields filled and the user sends it. The subject is the part that earns its place, because it routes the message before anyone reads it.
What the record carries
A recipient address, and optionally a subject and a body. A writing tool presents these as fields and encodes them into a mail record, which the URI format abbreviates to a compact form.
Tapping opens the mail application with everything filled in. As with a phone number, nothing is sent until the user sends it.
Why the subject is the point
An email tag with only an address is barely better than printing the address. The value appears when the subject carries information the sender would not know to include.
A machine identifier, a room number, a batch reference, an asset code. The message arrives already labelled, and it can be filtered, routed or matched to a record without anyone typing anything.
This is what turns a tag on a piece of equipment into a maintenance workflow: whoever finds the fault taps, writes a sentence, and the message lands with the equipment already identified.
The body, and why to keep it short
A prefilled body costs bytes on the tag and space in the message, and long ones tend to be deleted by the sender before they type anything.
A short prompt works far better than a template. One line asking what the problem is gets an answer. Six lines of structured form get ignored.
Remember that everything you prefill is also everything you can never change on tags already deployed. A body referencing a person or a team is a hostage to staff turnover.
Where it works well
Equipment fault reporting, where the subject identifies the machine. Building maintenance, where it identifies the room. Feedback points, where it identifies the location.
Where it works poorly is anything a member of the public is meant to use casually. Opening a mail application is a heavier action than opening a web page, and people abandon it more often. A link to a short form is usually the better tool for that audience.
It also fails for anyone whose phone has no mail account configured, which is more common than it used to be.
Frequently asked questions
Is the email sent automatically?
No. The message is composed and the user sends it, on both platforms. A tag cannot send mail on someone's behalf, which is the correct behaviour.
Can I put several recipients on one tag?
The format allows additional recipients, and support varies between mail applications. Test the exact devices in use, since a partially handled address list is worse than a single recipient.
Should I prefill the body?
Keep it to one short line if you do. Long templates cost tag space and get deleted, and anything naming a person becomes wrong when that person changes role.
What if the phone has no mail account?
Nothing useful happens, which is a real failure mode with a growing audience. Where that is plausible, a link to a web form reaches everyone.