For several weeks now when I try to send an email in emClient via Outlook the email ends up in the Local Folders Outbox and won’t transmit.
If this is an Outlook.com type acct, could be “you don’t have Airsync enabled” in your account setup.
Go to “Menu / Accounts” and select your account on the left. Then click the “General tab” along the top. Now in “Services” part way down see if you have ticked the box marked “AirSync”. If you haven’t, check that box and then save accounts.
If you already have AirSync enabled, then could be related to eg: too larger file attachments and the SMTP server won’t allow the message to send. Microsoft allow approx 20MB in size. So if you do have a large file attachment like that, you can alt send using eM Client “Cloud attachments” to send large files via eg: One Drive, Google Drive, Dropbox etc. See this link for info.
Now “if you don’t have large file attachments and your emails are stuck in the outbox”, then sometimes that can be related to background resident programs interfering with the outgoing mail such as eg: Optionally installed Antivirus programs or Optionally installed Firewall Security programs or VPNs. So if you have anything like that, try completely disabling those to test.
Now if you don’t have any optionally installed programs like that or disabling those made no difference, then could be “a possible corrupted account in eM Client” and you might then need to try removing and readding your Outlook account via the "automatic account wizard at the top of accounts.
Note: If you do try removing and readding your account, make a manual Backup first via “Menu / Backup” just incase you need to restore for any reason. You can see when the backup is complete in “Show Operations” via clicking the drop-down on the right of Refresh top left.
Now if removing and readding your Outlook account still cannot send mail, then update what your SMTP mail account settings are and also what version of eM Client you are running. Also if you are running Windows or Mac & OS version.