Are saying that the email now works? I agree, the provider settings at https://www.infomaniak.com/en/support/faq/2430/configure-thunderbird-in-imap-mail indicate the SMTP server from your post.

I added my Infomaniak email account to Thunderbird. The integration was successful, but I cannot send emails from Thunderbird Infomaniak unless I replace the outgoing server mail.infomaniak.com with smtp.gmail.com. Does anyone know what is happening?

The infomaniak instructions have a picture that indicates the TB setup wizard suggests SSL/TLS security on the outgoing smtp server, which would apply it on port 465. But further down the page the recommended setting for the smtp is STARTTLS security on port 587. Check Account Settings to confirm.

The infomaniak instructions have a picture that indicates the TB setup wizard suggests SSL/TLS security on the outgoing smtp server, which would apply it on port 465. But further down the page the recommended setting for the smtp is STARTTLS security on port 587. Check Account Settings to confirm.

Is this still the case?? I'm currently using port 465 using TLS/SSL and my mails are being sent without any problem. Please note that the use of STARTLS is discouraged by most experts out there because it creates an encrypted connection out of an unencrypted connection. The first handshake is done totally unencrypted, meaning it is a highly unsecured method of connection. Please provide feedback. Thanks in advance.

sfhowes said

The infomaniak instructions have a picture that indicates the TB setup wizard suggests SSL/TLS security on the outgoing smtp server, which would apply it on port 465. But further down the page the recommended setting for the smtp is STARTTLS security on port 587. Check Account Settings to confirm.

Is this still the case?? I'm currently using port 465 using TLS/SSL and my mails are being sent without any problem. Please note that the use of STARTLS is discouraged by most experts out there because it creates an encrypted connection out of an unencrypted connection. The first handshake is done totally unencrypted, meaning it is a highly unsecured method of connection. Please provide feedback. Thanks in advance.

I can't speak to the security concerns, and don't have an infomaniak account to test, but most providers require either SSL or STARTTLS security, but seldom both, in order to connect to their server. If you can confirm that the infomaniak smtp works on both port 465 and 587, that is worth pointing out.