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email bounce


How to fix  ‘553 sorry, unknown email address’ error in  Outlook, Thunderbird and Outlook Express

How to fix  ‘553 sorry, unknown email address’ error in Outlook, Thunderbird and Outlook Express

‘553 sorry, unknown email address’ is a common email error that happens because the recipient address is invalid. The senders would see this error in the bounce message they receive.

Error 553 is also called SMTP Error 5.5.3 and can happen irrespective of what mail server the sender is using – Exim, Qmail, Exchange, etc. (more…)