Answer first
Test webmail, check outbox, remove large attachments, review storage full warnings, confirm the password works, and note whether the issue affects one device or every device.
If webmail works, the mailbox is likely active and the issue may be inside the app or device.
Large attachments, full mailboxes, and stuck outbox messages can block send/receive.
Keep provider name, app name, device, error message, and whether incoming or outgoing mail is affected.
Quick FAQ
Why can I receive but not send?
Outgoing settings, large attachments, authentication prompts, or blocked outbox messages may be the cause.