Question: Are email addresses case sensitive?
Yes, In email address before the @, are case senstive. So email address is case-sensitive.
Question: What is the meaning of return-path, reply-to and from?
Return-path: If email is failed to deliver OR bounced, then email will return to return-path.From: <fromemail example.com=""> To: <you example.com=""> Reply-To: <replyto example.com=""> </replyto></you></fromemail>
Reply-to: If someone reply on email, then email will be goes to reply-to.
From: It denote from where which email-address came.
Question: What is the difference between ports 465 and 587?
Both are protocol.
465 is for SMTPS protocol, In this SSL encryption is started automatically before any SMTP level communication.
587 is for MSA protocol. SSL encryption may be started by STARTTLS command at SMTP level(if server supports). In this ISP does not filter server's EHLO reply.It helps to stop outgoing spam email.
Question: How to check if an email address exists without sending an email?
You can to execute below command.
This identifies the recipient of the email message. This command can be repeated multiple times for a given message in order to deliver a single message to multiple recipients.
Question: What are test email recipients?
OR
Which email address I can use for sending test email?
Following are testing email address
t11111@no-spam.ws
t11112@no-spam.ws
t11113@no-spam.ws
t11114@no-spam.ws
t11115@no-spam.ws
Check http://no-spam.ws/ for more email ids.
Question: How to check if smtp is working from commandline?
telnet {smtp_domain_name} {smtp_port}
