Until now the AI assistant in most firms has been a reader. It searched the document store, summarised the inbox and produced drafts for a person to move. That boundary is going, and with it comes the question of write access, an AI that can send email in the firm's name. On 7 July 2026 Anthropic expanded its Claude Cowork assistant to the web and to phones, and alongside that release its Microsoft 365 connection now offers what the company calls write tools. Switched on, the assistant can send email, manage drafts and calendar events, change mailbox settings and create or update files in OneDrive and SharePoint. Microsoft is building the same kind of action into Copilot across Outlook, Word and its other applications, and Google is doing likewise with Gemini in Workspace. Whichever vendor a firm has chosen, the direction is shared. The assistant is moving from reading your practice systems to acting in them.
What write access changes
An assistant with read access tells you what sits in a file. An assistant with write access files the document, books the meeting it mentions and sends the reply. The appeal is plain, because routine correspondence and diary management absorb hours of a fee earner's week that no client wants to pay for. The shift in risk is equally plain. An email leaving a solicitor's mailbox is the firm's correspondence whatever drafted it. It can concede a point, misstate a position, give something close to an undertaking or reach the wrong recipient, and it does so at machine speed. A drafting error that a person would have caught on the way out of the door now has a route past the door entirely.
Read the safeguards before you switch anything on
The controls that ship with these features tell you what the vendors themselves worry about, and Claude's are a useful worked example. Write tools stay blocked for existing organisations until an administrator enables them. The assistant holds delegated permissions only, so it reaches nothing the individual user was not already allowed to see. Email it sends carries an attribution header identifying it as agent-initiated. Each user faces limits on writes, sends and recipients, attachments are refused outright, and every action is recorded in the Microsoft 365 audit log. Those are sensible defaults, and they give a firm a checklist to put to any supplier offering something similar. Ask whether action features are off by default, what the tool can reach, how its actions are marked, what limits apply and where the audit trail lives. A vendor without clear answers has answered the question anyway.
Responsibility does not travel with the tool
An attribution header tells the recipient a machine pressed send. It does not move an inch of responsibility. The SRA expects a solicitor to stand behind work done with AI in the same way as work done by a junior, a point the courts have been making with growing impatience in the hallucination cases. Correspondence is no different from a filing in that respect. Supervision has to reach the new surface. A draft in an outbox invites review, a sent email forecloses it. The sensible pattern for legal work is to let the assistant prepare and a person release, at least until the firm has evidence of how the tool behaves. On matters where an error would be serious, keep write access off altogether. We covered the supervision questions raised by autonomous assistants in when your AI assistant works while you sleep.
What a firm should do
Treat write access as a decision, not an upgrade. Leave it off until you have decided which roles gain anything from it, then enable it user by user rather than firm-wide, starting with people whose work is low risk and well supervised. Prefer draft-and-review over direct sending wherever the tool allows it. Check the audit log weekly for the first month, because how the assistant behaves in your firm's hands matters more than any product page. Write the boundary into your AI use policy so staff know what the assistant does in their name, an exercise we set out in writing an AI use policy your team will follow. Be ready, too, to tell clients how it touches their matter. The firms that get value from this will be the ones that granted authority the way they would to a new member of staff, a little at a time, with someone watching.
The access-control basics behind all of this are covered in the NCSC's small business guide.
Before any tool sends a word in your firm's name, the boundary deserves an hour of proper thought, and we help firms draw it: get in touch.