Fastmail SMTP server setting is necessary for sending an email. When you configure Fastmail on your device you face the issue that you are not able to send your emails. In such a scenario you are required to configure SMTP outgoing server settings on your device. Provide the following information:
Outgoing server hostname: smtp.fastmail.com
Provide your fastmail email address including specific domain name in the username field.
Enter your fastmail password in the password field.
Enter 465 or 587 as SMTP port number.
Select TLS/SSL required yes ith port number 465 and no with port number 587.
Select STARTTLS required no with port number 465 and yes with port number 587.
Once you have configured these settings you are able to send your emails. Some devices have inbuilt settings so you need to check your settings once. if you can face than contact fastmail technical support number 1-855-925-7079 and get the reliable support