For the Mail Gateway service, you can set limits for mail that is received and delivered. To help prevent against Denial of Service (DoS) attacks, you can also set limits on the number of inbound and outbound connections.
Configure Mail Gateway Service Limits
- Go to CONFIGURATION > Configuration Tree > Box > Virtual Servers > your virtual server > Assigned Services > Mail-Gateway > Mail Gateway Settings.
- In the left menu, select Limits.
- Click Lock.
In the Mail Gateway Limits section, set limits for mail that is received and forwarded. You can configure the following settings in this section:
Limit Mail Data Size
To limit the size of mail data (attachments), select yes. In the Mail Data Size (MB) field, enter the maximum size for mail data.
Mail Data Size (MB)
The maximum size of mail data in MB (default: 20). If the mail size exceeds this limit, the mail gateway refuses delivery and sends an error message to the sender.
DSN for Max Data Size Excess If you want the mail gateway to create an extended Delivery Status Notification (DSN) message when an email has exceeded the maximum allowed size that is specified by the Mail Data Size (MB) setting, select yes. Maximum Number of Recipients The maximum number of recipients of mail. Because RFC2821 requires at least 100 possible recipients of mail, you cannot enter a limit that is lower than 100 (default: 200). DSN for Max Recipients Excess
If you want the mail gateway to create an extended DSN when an email has been forwarded to more recipients than the limit specified by the Maximum Number of Recipients setting, select yes.
Refuse Empty Mail from
By default, the SMTP server accepts all incoming emails. To reject emails with empty sender information, select yes.
Accept Loose Domain Name
Domain names may only contain the following characters: [-.0-9A-Za-z]. From the Accept Loose Domain Name list, select one of the following options to specify if domain names are checked for incorrect syntax.
- no – Domain names are checked. Emails are rejected if their domain names use incorrect syntax.
- yes – Domain names are not checked. Emails with domain names that use incorrect syntax are delivered.
The maximum number of to-be-scanned attachments per MIME email.
Drop Mails over Attachment Limit
To drop emails that contain more attachments than the limit specified by the Max. Attachments setting, select yes.
Drop Fragmented Mails
To reject malformed and damaged emails, select yes.
Max Age of crashed Mails (d)
The maximum number of days that emails can stay in the 'crashed' directory.
Max. SMTP Line Length
The maximum number of characters per line. Barracuda Networks recommends that you use the RFC maximum limit of 1000 characters.
Max. Received From Lines
The maximum number of From: headers. Default: 20.
Max. Header Lines
The maximum number of header lines. Default: 100.
In the DoS Protection section, set limits on the number of parallel inbound and outbound connections. You can configure the following settings in this section:
Parallel Inbound Connections |
Parallel Outbound Connections
The maximum number of parallel inbound or outbound connections for receiving mail (default: 5). If your mail gateway handles a lot of mail traffic, you may need to increase this value. (These values must not be 0.)
Parallel Outbound Connections |
Parallel Outbound Conn. per Peer
The maximum number of parallel TCP connections from a single inbound or outbound source IP address (default: 25). This provides effective protection against DoS attacks.
- Click Send Changes and Activate.
Continue with How to Configure Mail Gateway Reporting.