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Microsoft 365 Email- Unable to Send Emails (Login to server failed)

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  • Last reply by tom469

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We just signed up for a Microsoft email account this weekend. Preferring to use TB, everything seemed ok as I was able to receive emails just fine, but upon trying to send emails, I continue to receive an error message saying "Login to server smtp.office365.com with username tom@callablefirst.com failed".

I have gone through many different troubleshooting techniques I read about in the community and here is a checklist of things tried:

1. Checked that IMAP is toggled on in 365 admin 2. Checked that TB is accepting cookies and no exceptions are listed 3. Tried changing SMTP server to recommended instructions from Microsoft and verified all settings are OAuth2 4. Enabled 2F Authentication 5. Used config. edit to clear out all existing OAuth2.scope files

I have downloaded a different email client- eM client and everything works fine sending emails from that end so I am convinced this has nothing to do with my password being entered incorrectly, but some unknown conflict that isn't getting resolved between TB and the 365 account. I prefer using TB but am getting to the point where this is taking a lot of time away from other business activities that need to get done.

I have my marketing guy trying to remotely help figure things out, too, but he is at a loss as well.

Let me know if you have any ideas, thanks, much!

We just signed up for a Microsoft email account this weekend. Preferring to use TB, everything seemed ok as I was able to receive emails just fine, but upon trying to send emails, I continue to receive an error message saying "Login to server smtp.office365.com with username tom@callablefirst.com failed". I have gone through many different troubleshooting techniques I read about in the community and here is a checklist of things tried: 1. Checked that IMAP is toggled on in 365 admin 2. Checked that TB is accepting cookies and no exceptions are listed 3. Tried changing SMTP server to recommended instructions from Microsoft and verified all settings are OAuth2 4. Enabled 2F Authentication 5. Used config. edit to clear out all existing OAuth2.scope files I have downloaded a different email client- eM client and everything works fine sending emails from that end so I am convinced this has nothing to do with my password being entered incorrectly, but some unknown conflict that isn't getting resolved between TB and the 365 account. I prefer using TB but am getting to the point where this is taking a lot of time away from other business activities that need to get done. I have my marketing guy trying to remotely help figure things out, too, but he is at a loss as well. Let me know if you have any ideas, thanks, much!
Attached screenshots

Chosen solution

I have an update and a solution that worked. I am not sure why it worked but here is what I did to solve the problem:

1. Install a 2nd instance of my account under POP3

That was it. Suddenly, I was able to send emails, including from the IMAP account.

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You shouldn't be seeing that kind of password prompt if the authentication is OAuth2. See if you have other smtp servers for the account with 'normal password' authentication, and remove any smtp:// or imap:// entries from Saved Passwords in Settings, restart TB, enter the account password in the OAuth dialog.

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Thanks for the suggestion. I deleted the smtp and imap entries and there were none with "normal password" settings set. Restarted TB and still encountering the same issue and message.

Helpful?

more options

Chosen Solution

I have an update and a solution that worked. I am not sure why it worked but here is what I did to solve the problem:

1. Install a 2nd instance of my account under POP3

That was it. Suddenly, I was able to send emails, including from the IMAP account.

Helpful?

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