I did a search on this forum and tried several of the suggestions but non appeared to work. Some email providers (such as your ISP or even Gmail) won't let you send messages larger than a certain size. Adding pictures and large attachments to your message can prevent you from sending that message (and any messages sent Fix Outlook and Office365 Sync Issues after the large message). If you’re using cPanel, Outlook is most likely setup with POP3 account or IMAP. I’ve seen some providers have issues when auto Send/Receive is set to less than 5mins. Outlook accounts can have up to 100GB of storage per mailbox.

Repair your classic Outlook program

It includes a listing of your accounts, autocomplete information, and your name and initials. To repair your Outlook profile or create a new one, see Fix your Outlook email connection by repairing your profile. Go to your Outbox and then open the stuck email messages. If that message has an attachment that's larger than 20MB, delete the attachment and either attach a smaller file online Outlook email repair utility or attach a link to the attachment. For more information, go to Reduce attachment size to send large files with Outlook or Exchange Online limits.

Make sure you are connected to the Internet

But every once in a while, the Microsoft filters get it wrong and accidentally label a normal email as spam. To start Outlook in safe mode, press the Windows key on your keyboard. In the search box, type outlook.exe /safe, then press Enter.

Check your blocked users list

If you've changed your password on the website for your email account, you'll need to change it in new Outlook, too. Sign up for tips and industry insights to level up your emailing skills. Outlook lets you block a sender or a domain in just a few clicks. This is a great way to protect your inbox from spammers and cyberbullies. If an email triggers the spam filters, Microsoft automatically moves it to your junk folder.

Create a new Profile

But if you’ve never cleaned your inbox, then you might have maxed out your storage limit. So if you’re waiting for an email from someone, you may want to check if the sender is registered on your blocked users list. But still, it’s worth checking if other users are currently experiencing similar issues with Outlook. Microsoft comes with a great option called Work Offline.

Can't send mail in Outlook.com

• Sometimes, an Outlook add-in will crash and prevent your email messages from sending.
• But still, it’s worth checking if other users are currently experiencing similar issues with Outlook.
• Occasionally, the Outlook program may need to be repaired.
• We've presented the methods in order of quickest to most in-depth.
• For more information, visit Add an email account to Outlook for Windows.
• For more information, go to Reduce attachment size to send large files with Outlook.
• To repair your Outlook profile or create a new one, see Fix your Outlook email connection by repairing your profile.
• You can repair this file by running the Inbox Repair Tool.

For more information, visit Add an email credential loop in Microsoft 365 account to Outlook for Windows. If that doesn't fix the problem, see the next section. To get help and troubleshoot other Microsoft products and services, enter your problem here.