It is now legal for agendas to be circulated by e-mail, however, as far as I am aware, councillors must decide for themselves whether or not they wish to receive them in this way. I'll try to find the exact wording.
If you're using the current model standing orders, they include an opt-in clause:
a The Proper Officer shall:
i. at least three clear days before a meeting of the council, a committee or a sub-committee,
serve on councillors by delivery or post at their residences or by email authenticated in such manner as the Proper Officer thinks fit, a signed summons confirming the time, place and the agenda (provided the councillor has consented to service by email)