"access only by" is a grammatically correct phrase and can be used in written English.
It is typically used to indicate that something can only be reached or obtained in a specific manner, such as through a certain route or with certain qualifications. Example: "The secret garden was accessible only by a hidden path through the woods."
The bus can establish Internet access only by stringing a telephone cord to a telephone jack nearby.
None of these uses would be possible if the owners of the proxy servers made sure to configure them for access only by authorized users.
And it suggests that this meeting took place somewhere in a mythic six-star hotel (access only by helicopter) in its own spacious grounds, surrounded by high walls with guards and checkpoints.
"And I said, 'I don't know that music.' And he said, 'Wally, you're gonna love this.' " Years later, De Backer wrote a tribute song for Perrey, using an Ondioline he could access only by flying from Melbourne to the Audities Foundation, an electronic-instruments archive in Calgary, Canada.
We can expect, at its worst, perhaps a Soviet-style blockade of information, and access only by TV news apparatchiks willing to deliver the latest in sanitized boosterism for President Trump every night.
Usually, Mr. Bailey said, that is done by using locked mailboxes that can be accessed only by tenants and postal workers.
It also has its own quay and moorings and can be accessed only by footpath or boat.
Surrounded by a high wire fence, and accessed only by a huge steel security gate, it is a vast site that took me an afternoon to wander through.
One chapel is accessed only by a ladder up a rock face, others are tucked inside natural niches or at the foot of huge crags.
The lower bowl of the stadium can be accessed only by forking over ludicrous sums of money to the ticket office.
We ride the elevator in respectful silence to the second floor, which can be accessed only by the turn of a key on Mickey's key chain.
