Compose mails

How to compose a mail?
Why cannot I send mail to other sites?
How do I take a screenshot when I compose?
Can I send attachments of the same size as the limit?
How long does it take for the other party to receive my mail?
How many people can an email be sent to at the same time?
Why cannot I send a mail to any email address of any format?
Can my mailbox connect with other mailboxes in the world?
How can I guarantee that the outgoing mail will allow the recipient to read it normally?
My mail has not been written yet. Can I save it first and send it later?
Can I send multiple attachments in one email?
How to use automatic signature?
What is "Multimedia"?
What is a "Read receipt"?
What is "Urgent"?
How can I also save a copy of the mail in the "Sent" folder?
How to schedule sending?
How to modify or cancel the scheduled mail to be sent?
What should I do if I receive a system bounce after sending an email?
Why cannot the other party receive the email I sent him?
Why are the content of emails cleared after I press "Esc"?
How to use drag and drop attachments?