I too have blockchain.info wallet for too long,, I never received any kind of these emails from them so which is obviously scam attempt by the people but I wonders how they know you email address which is used to login for the blockchain wallet?
They usually collect email address from the spreadsheet of bounty campaign.
Keep separate email for wallet purpose which needs to be anonymous and just use only for online wallets to restrict these emails.
Just a tip if you are logged into that mail into your android check for the application which has no icon and name which will be at the last of installed application which is the scammer's thing to hack your phone.
Thanks for the advice though I do as you mentioned. That's why I could stay safe and can know about their phishing email.
Though it wasn't about the airdrop, I'd like to share here the email I received since it's another attempt in hacking Blockchain.com wallets. I didn't bother downloading the attachment to see what's in there, obviously it's a phishing attempt considering the email address from where it came and the need of 12 word seed phrase.
It is obviously another scam attempt. Blockchain will never ask you seed to verify and without doing so they will suspend your account. Actually, they will never ask you to provide seed. They can only ask if you can't log in and want to log in by the seed.
) seeing as how blockchain.com really did have a $20 Stellar giveaway. 
