Hi ! Thanks to Jade Liang for taking interest in my problem! I modified the title. Now the problem is only about my usual mailbox, firstname.lastname@example.org. My gmail mailboxes are now functionnal. I kept to try with the same parameters that I know are the good ones, 993 and 465 ports, SSL/TLS, that failed and suddenly it worked! No explainations... But not my email@example.com... My two others PCs that run Outlook and connect regulary to my firstname.lastname@example.org use Office 2010 Pro. I updated Office, the version of Outlook is Microsoft Outlook 2019 MSO (16.0.13801.20240) 32 bits. I cleaned my profiles. I tried to add the account from Outlook and also from the control panel, with no effects. I can connect to smtp.bbox.fr using telnet on 25 port, launch usual commands, as on pop.bbox.fr on 110 port, and on imap.bbox.fr on 143 port. I tried with Thunderbird and Mailbird. With each I initially tried the automatic configuration. Thunderbird gave me a 143/25, no secure protocol. If I try to change any parameter it fails to connect. Mailbird produced something nice : imap4.bbox.fr, 993, SSL/TLS, smtp.bbox.fr, 587, SSL/TLS and woks nicely I suspect the bbox server - IBM software, "CAPABILITY IMAP4rev1" - being a bit strange, and I can't get help from the provider - he says that he is not responsible for problems with outlook... I looked at the Events journal. In "Applications" I don't see anything significant, if not a Warning, ID 36 : "Search ne peut pas effectuer l’indexation des données Outlook. Impossible de continuer l’indexation pour C:\Users\moi\AppData\Local\Microsoft\Outlook\email@example.com(3).ost (erreur=0x80340800). Si cette erreur persiste, contactez le support technique Microsoft." A bit complicated... I use this address since twelve years. Sure, it was not a big choice. It is the one I made... Changing an e-mail address is more ennoying than a physical address. You get necessarily more correspondants than you had before.