Bulk spam could be a thing of the past in as little as three years the CEO of email security vendor Brightmail, Enrique Salem has predicted.

The bad news is that he believes that inbox spammers will increasingly target users through 3G mobile services, exploiting the increasing popularity of email-to-phone communication.

Salem has been touring Europe to promote the company’s recently-announced anti-spam technology, “Brightmail Reputation Services”, which is being positioned as complimentary to spam-killing email authentication technologies such as Microsoft’s Caller ID for Email, Yahoo’s Domain Key system and Sender Policy Framework (SPF).

Each of these is being promoted as the way to stop spam by making it technically impossible for spammers to hide themselves using spoofed domains and fake email addresses.

Statistics on companies abusing the system by bulk sending emails or upsetting large number of users could be easily spotted by Brightmail’s Reputation Services, leading to them being banned. This would also make it difficult to send viruses because these too would need to authenticate their point of origin.

Caller ID, in particular, has been attracting major interest and was given a high-profile promotion by Bill Gates at this week’s RSA Show in San Francisco. Under the scheme - which is similar in its inner workings to the rival SPF proposal - it would be possible to verify that messages sent from a domain really originated there.

“If you are not willing to publish using SPF or Caller ID then an ISP is not going to send your email,” said Salem. Brightmail would support Caller ID, but remained open-minded. “I think there will be multiple standards. It may evolve to one standard, over two to three years,” he said.

These ideas sound promising, but some uncertainty remains. SMTP-based mail servers will have to be upgraded and that is bound to add cost.

“Spam exists because of the SMTP protocol but the notion of replacing SMTP is not practical. What we have to do is build on top of it,“ Salem insisted. ISPs and their customers were driving the demand for changes to SMTP and would absorb the cost for the sake of its long-term benefits.

Faced with a narrowing of options, spammers might try to target people through email-to-mobile gateways where users would find it harder to identify and therefore complain about domain abuse. According to Salem, mobile operators had expressed concern about this issue at this week’s 3GSM World Congress. “I’m not predicting spammers will stop sending spam," he said, "spam will still be sent but it will not get to your inbox.”