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Understanding the Connection Log / SMTP protocol | MaxBulk Mailer ▸ Frequently Asked Questions

Understanding the Connection Log / SMTP protocol

MaxBulk Mailer ▸ Frequently Asked Questions

Compatible with MS Windows Compatible with MacOS


Understanding the Connection Log / SMTP protocol

In order to understand MaxBulk Mailer "Connection logs" you need to read RFC 821 (Request for Comments 821). It is a technical memo about SMTP protocol implementation. (SMTP stands for SIMPLE MAIL TRANSFER PROTOCOL).

SMTP protocol is a text protocol where a SMTP client (MaxBulk Mailer) talks to a SMTP server. Basically this conversation looks like this (This example shows how the client connects, send the sender data, then the recipient data and finally the message itself):

Server:
220 SU-SCORE.ARPA Simple Mail Transfer Service Ready
Client:
HELO MIT-MC.ARPA
Server:
250 SU-SCORE.ARPA
Client:
SEND FROM:<EAK@MIT-MC.ARPA>
Server:
250 OK
Client:
RCPT TO:<Admin.MRC@SU-SCORE.ARPA>
Server:
450 User not active now
Client:
DATA
Server:
354 Start mail input; end with <CRLF>.<CRLF>
Client:
Blah blah blah...
Client:
...etc. etc. etc.
Client:
.
Server:
250 OK
Client:
QUIT
Server:
221 SU-SCORE.ARPA Service closing transmission channel

MaxBulk sends commands like:

HELO <domain>
RCPT TO: <forward-path>
DATA
SEND FROM: <reverse-path>
QUIT

The server always answer with a 3-digits code and a message. For example:

211
System status, or system help reply
220
<domain> Service ready
221
<domain> Service closing transmission channel
250
Requested mail action okay, completed
251
User not local; will forward to <forward-path>

and if an error occurs, the server message always starts with a 4xx or 5xx code like:

421
<domain> Service not available, closing transmission channel
450
Requested mail action not taken: mailbox unavailable
451
Requested action aborted: local error in processing
452
Requested action not taken: insufficient system storage
500
Syntax error, command unrecognized
501
Syntax error in parameters or arguments
502
Command not implemented
503
Bad sequence of commands
504
Command parameter not implemented
550
Requested action not taken: mailbox unavailable
551
User not local; please try <forward-path>
552
Requested mail action aborted: exceeded storage allocation
553
Requested action not taken: mailbox name not allowed
554
Transaction failed

For more information take a look at the SMTP response code list.

Written by Stanley Roche Busk
for Maxprog, LLC







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MaxBulk Mailer is a full-featured and easy-to-use bulk mailer and mail-merge software for macOS and Windows that allows you to send out customized press releases, prices lists, newsletters and any kind of text or HTML documents to your customers or contacts.

MaxBulk Mailer is fast, fully customizable and very easy to use. MaxBulk Mailer handles plain text, HTML and rich text documents and gives full support for attachments. With MaxBulk Mailer you will create, manage and send your own powerful, personalized marketing message to your customers and potential customers.

Thanks to its advanced mail-merge and conditional functions you can send highly customized messages and get the best results of your campaigns. You also have support for international characters, a straightforward account manager with support for all type of authentication schemes including SSL, a complete and versatile list manager, support for importation from a wide range of sources including from remote mySQL and postgreSQL databases.

MaxBulk Mailer is a software tool that you purchase once, no need to pay on a per-email basis to submission services!

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