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Infrastructure Division of Information Technology

Messaging Services

SMTP Relay Configuration


Maximum message size

This limits the size of messages that the relays will accept to 50MB.

Maximum number of recipients

The relays will accept messages with up to 100 recipients.

Outbound message processing

The Proofpoint appliances used for do regular garbage collection on the anti-spam/anti-virus processes. When a node is doing housekeeping, SMTP is still running, but because the anti-spam/anti-virus processes are not available, the SMTP service responds with SMTP "421 4.7.0" I'm busy, try again later messages. Many applications and appliances do not handle an SMTP 4xx gracefully and most end up losing the message.

While the mail servers lived on campus, it was common for these applications and appliances to hand off messages to those servers. As part of decommissioning of the email complex, was set up for use by applications and devices to hand off email without having to meet the formal correctness requirements of the actual, internet-facing relays.

If you have devices that need to email but have problems talking to, please point them to port 25.

SMTP Authentication (SMTP AUTH)

All Texas A&M NetID account holders can configure a single out-going SMTP server using SMTP Authentication (AUTH), regardless of being on- or off-campus or their Internet Service Providers SMTP servers. The username and password for AUTH are a user's NetID and respective password. As with all areas where NetID use is possible, the connection MUST be encrypted (the option to use will be listed as "TLS" or "STARTTLS").

If your client supports it, please use the mail submission (MSA) port 587.

Available SMTP AUTH ports on are:

  • support AUTH via STARTTLS on port 587
  • support AUTH via SMTPS on port 465
  • support AUTH via STARTTLS on port 25 (not recommended)


We are not yet publishing SPF or DKIM records, but we are considering them in the SPAM scoring process.

Virus Scanning

  • The relays use F-Secure Anti-Virus technology.
  • Incoming or outgoing email that tests positive for a virus is discarded.

Spam Filtering

  • The relays use Proofpoint's MLX machine learning technology to score messages.
  • Email with a spam score greater than or equal to 50 is quarantined.

The spam quarantine is

  • Digests are sent at 9:00 am and 3:00 pm, daily, to the message recipient.
  • The digest provides links to the quaratine so that the message recipient can view and/or release messages.
  • Additional options, such as message deletion, sender safe-lists, and sender block-lists, are available from the link to view an individual's spam quarantine.
  • Quarantined messages will be held for 14 days defore being deleted.

Overrides to Spam Filtering

An override that cannot be handled by a personal safe-list, such as a PDR or MLX override, can be overridden by Texas A&M IT. This safe-lists all email from that server and so will be implemented only after due consideration. Email or call Help Desk Central (979.845.8300) to request administrative intervention.