Manx Telecom is apologising to customers following failings with its e-mail service.
People have been complaining that outgoing mail hasn't been reaching its destination.
MT says the problem has been caused by some manx.net accounts holding weak passwords - something being exploited by outside companies to send large amounts of spam.
Users are now being asked to create secure and strong passwords, as many are likely to be unaware that their account has been compromised.
MT says incoming mail remains unaffected.
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