a mobile phone issue ?
I explicitly have no email on my mobile phone ...I do have several public email accounts, i.e. yahoo, gmail etc. which store your private emails on their servers. The problem with gmail so far has not occurred on my computer using Thunderbird with imap.gmail.com and SSL/TLS.
That could mean that the email client on your mobile phone has been compromised inside Android / iOS , or as the hack involves ponying up a new telephone number, that a couple of mobile telecoms providers are invaded on their side with malicious hacks.