By Diane Bartz

WASHINGTON, Feb 11 (Reuters) - Blix, which sued Apple Inc for excluding its BlueMail product from the Mac app store, said on Tuesday that it was being allowed back in the digital shop.

After BlueMail was removed from the app store eight months ago, Blix filed a lawsuit against Apple that accused the hardware giant of infringing its patented technology and abusing its dominance in the app store.

Blix, which was founded by Ben and Dan Volach, had reached out to other app developers to encourage them to work together to counter Apple's considerable power.

"When we wrote to Apple’s developer community, BlueMail was back on the App Store within a week," said Dan Volach, co-founder at Blix. "If you’re out there too scared to come forward, let this be your proof that speaking out works."

Apple has said that Blix updated the BlueMail software, which Apple had said would potentially expose users' computers to malware and threaten the users' privacy. This security issue was the only reason the BlueMail software was excluded from the Mac app store, according to an Apple spokesman.

The Mac App Store sells software for Apple's personal computers and is separate from the much larger App Store that Apple operates for mobile devices such as iPhones and iPads. Unlike iPhones and iPads, where users can only install third-party software via the App Store, Mac computers can bypass the Mac App Store and download third-party software directly from the internet, although the process takes more steps. Blix's software was not removed from the App Store for iPhones and iPads.

Separately, Apple is one of four tech giants that are under investigation for alleged anti-competitive behavior. The others are Alphabet's Google, Amazon.com and Facebook, and the probes are being carried out by the Justice Department, Federal Trade Commission, state attorneys general and House Judiciary Committee.

The U.S. Justice Department has reached out to app developers as part of its investigation, according one of the developers and another person familiar with the investigation.

As the arbiter of who is allowed to sell in the app store, Apple says it has the responsibility to ensure that only the highest quality apps are sold there. (Reporting by Diane Bartz and Stephen Nellis; Editing by Steve Orlofsky)