Though Rouhani's English-language Twitter account is unverified, it is controlled by his campaign team, who were confirmed to have issued the tweet.
It is believed that the account is kept semi-official for the purposes of communicating with Western media and those outside Iran. Such is the case for many Iranian officials, most of whom don't publicly acknowledge their accounts, as the country blocks such social media services internally.
The new president is universally considered to be more moderate than his predecessor Mahmoud Ahmadinejad, known for his notoriously anti-Israel and anti-Semitic rhetoric.
The message from Rouhani appears to soften the country's position, not just addressing Iran's Jewish population of some 25,000, but "all Jews." Though the tweet is hardly a declaration of peace, it stands in stark contrast to previous leadership.