To use your brain!
The Supreme Court has just stated, in Barton v Wright Hassall, that a claim form should not be served on a solicitor by e-mail.
Solicitors for the other side will do whatever they can for their clients. That makes sense, so don’t hold it against them.
So when they e-mail you, they know that you, a LIP, will likely accept that e-mail as good service (or to test whether you will) and it may entice you to use only e-mail too. That said, most solicitors know better than to be this deliberately devious.
When you’re a LIP, you have to THINK, for chrissakes! (And always, always, always check the CPR.)
E-mail is neither reliable nor secure. Neither is normal postal mail. (Hand either one of certain postal carriers a fiver and your envelope will disappear. That’s the reality of every-day life in Britain. If you don’t know that, you’re either dead or asleep at the wheel.)
Never ever use anything less than a courier service or Royal Mail special delivery for vital documentation to lawyers or other parties to a case (or the court). Then CHECK that it has actually been delivered and download and print that confirmation.
(Or, hand-deliver, and make sure you have a name, signature, role of the person, and time and date of the delivery and description of the delivered document on a form. That might work too.)
And that’s apart from the fact that serving a claim form on a solicitor sounds like a ridiculous idea to me. The court issues claims.
NOTE: I wrote all of the above without having a clue of what this particular case (Barton v Wright Hassall) was about.