This seems to be caused by Adguard HTTPS filtering. Disabling Adguard should allow Mailbird SMTP STARTTLS connections to complete without issue and the emails to send properly.
Articles in this section
- Mailbird freezes or hangs
- I cannot send/receive emails anymore
- I am unable to add my email account in Mailbird/ "Authentication failed" message
- I can't receive or send email anymore
- Problem installing or setting up
- Having trouble sending E-mails?
- Mailbird is installed, but there's no icon in the Start menu and a desktop icon
- Database version mismatch error
- AOL / Yahoo possible authentication issue
- I am unable to install Mailbird