Member Avatar for PhoenixInsilico

I have an account in an mail server with email address eg. but it does not allow sending more than 100 mails per day. Can I use postfix server to send mails on behalf of

  • 2 Contributors
  • 1 Reply
  • 392 Views
  • 13 Hours Discussion Span
  • Latest Post Latest Post by kc0arf

Dani AI

Generated

Short answer: yes — Postfix can send mail that uses a different From address, but only when the sending server is authorized to deliver for that address. 's upstream account that is limited to 100 messages/day means relaying through that provider will still be subject to the same quota. As noted, sending mail from an address without proper authorization (or without correct DNS/auth records) risks DMARC/SPF failures, spam classification, and blacklisting.

A practical, standard approach is to make Postfix an authenticated smarthost that submits via the legitimate SMTP server (or a paid transactional SMTP service). Minimal main.cf additions look like:

relayhost = [smtp.upstream.example]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_security_level = encrypt
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

And /etc/postfix/sasl_passwd contains a line like:

[smtp.upstream.example]:587 amiyatulu@example.org:password

Run postmap /etc/postfix/sasl_passwd, secure the file (chmod 600), and reload Postfix. To rewrite local senders so the From header/envelope shows the desired address, use sender_canonical_maps or smtp_generic_maps depending on whether the rewrite should happen on submission or only when delivering to remote hosts.

Deliverability caveats and alternatives: ensure SPF includes the sending IP or provider, sign outgoing mail with DKIM (Postfix needs an external signer like OpenDKIM), and have a proper PTR/HELO for the sending IP. If traffic needs exceed the provider quota, request a higher limit from the provider or use a reputable SMTP relay (SES, SendGrid, Mailgun, etc.) rather than attempting to forge senders — that keeps reputation intact and avoids violating terms of service.

Member Avatar for kc0arf

Postfix is a back-end email manager, like Exchange Server or Sendmail and not a front-end like Thunderbird or Eudora.

You may wish to also consider why you want to violate your terms/contract with your ISP.

Also, setting up another email server may not be as easy as you think. Yes, the technical software of an email server is easy to get and install, but email follows definitions bound in DNS records (specifically the MX record) and a number of us system administrators check each email message, and look for a defined MX record. If you don't have a valid email server address, and other pieces put into place, your message gets marked as spam, and eaten. If you do too much of this, other consequences, such as being blacklisted by an organization, can get you into real trouble.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.