SMTP & API
What Is the Difference Between SMTP, IMAP and POP3?
SMTP, IMAP and POP3 are the three protocols that move email around the internet, and each has a single, distinct...
Read moreCan SMTP Receive Email?
Strictly speaking, SMTP receives email at the server level — it’s how mail servers accept incoming messages from other servers....
Read moreWhat Is SMTP Error 554 and How to Fix It?
SMTP error 554 is a permanent rejection: the recipient server refused to accept your email. The good news? Once you...
Read moreIs SMTP protocol reliable?
Yes — SMTP is one of the most reliable application protocols on the internet. It runs over TCP, supports retries,...
Read moreWhich SMTP port to use?
SMTP uses several ports, but only two of them really matter for sending email today: 587 (with STARTTLS) and 465...
Read moreHow Does the Mailpro API Work?
Mailpro’s API lets developers send transactional and marketing emails directly from their software, without going through the web interface. Access...
Read moreHow Do I Send Emails with an SMTP Server?
Sending email through Mailpro’s SMTP server takes about ten minutes from start to first message. The exact steps depend on...
Read moreHow to Manage Unsubscribe Link for SMTP Messages?
Even when you send through SMTP from your CRM or your own application, every commercial message in 2026 must include...
Read moreHow Are Statistics Collected from an SMTP Sending?
An SMTP send is fast and silent: your application hands the message off, the relay delivers it, and unless something...
Read moreWhere Do I Find the SMTP Authentication Credentials in Mailpro?
To send messages through Mailpro’s SMTP relay you need four pieces of information: server host, port, username and password. They...
Read moreWhat Type of SMTP Server to Choose?
Choosing the right SMTP server is one of the most consequential technical decisions for any business that sends email at...
Read moreWhat Is the Maximum Weight of a Message Sent Through SMTP?
Mailpro’s SMTP relay accepts messages up to 20 MB total, including the email body, headers and all attachments after Base64 encoding...
Read moreWhat’s the difference between SMTP and API?
Both SMTP and a transactional Email API send messages from your application to your customers, but they take different paths...
Read moreWhat Is an SMTP Server? How SMTP Relay Works and Why You Need It
An SMTP server (Simple Mail Transfer Protocol) is the dedicated server that handles outgoing email. When your application, CRM or...
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