Hi @vlatik ,   If you're able to send an email using our post office it means the e-mail works find, we recommend to perform a full scan on your PC/Laptop it could be caused by potential malware. In the event that you performed this before, send me your account details (Username/Customer ID together with the address on file) also include the affected email address and we'll raise this to our postmaster for further investigation.   How do I private message (PM) in the community    Regards,   @vlatik wrote: Hi,   All of a sudden my Outlook stopped sending emails. Still receiving them but on send get an error: The following recipient(s) cannot be reached: 550 5.7.1 <email address>... Relaying denied. IP name possibly forged   I've looked through the same issue other people had on this site. My settings did not change and are all correct, so it must be something on your end. Tried sending test email through post office and it worked. But cannot send anything in Outlook.   Thanks.   ... View more