Spam protection

SpamAssassin is a powerful mail filter, which uses text analysis to determine the probability of a mail message being spam. Some of the factors for this decision are the presence of HTML parts in the mail, phrases common for spam ("drastically reduced", "save big money", etc.), excessive HTML comment tags (often used to 'hide' common phrases from mail filters), invisible text (using the same foreground color as the background color) and many others. Each occurrence of something suspicious raises the probability of the message being spam (the spam level). You can configure the spam level above which the mail messages will be filtered. The levels manage how strictly SpamAssassin reviews each message to consider whether it is spam or not. Setting the spam level to a low value (1/10) will probably cause legitimate mail to be filtered. Setting it to a high value (10/10) may let some spam into your mailbox. The optimal level depends on the contents of the mail you receive - you will have to adjust it until you find the lowest level possible, at which no legitimate mail is filtered (you might need to check regularly your Junk mail folder to see if you have legitimate messages filtered). You can find step-by-step instructions on how to enable SpamAssassin or change the spam level in our Enable SpamAssassin article. Statistics show that 5/10 is generally the optimal spam level. It usually does not result in filtering legitimate email, while it is still efficient against spam. However, we do recommend that you check your Junk mail folder regularly, in case there are filtered legitimate messages. Enabling SpamAssassin globally will make it process any message, sent to your domain, while enabling it per user basis will make it scan only the messages, destined for the respective mailbox. Depending on your Junk Mail folder setting, the filtered messages are delivered to your Junk Mail folder or simply deleted. You can read more about this folder in our Junk Mail folder article. If the SpamAssassin filter is enabled for a mailbox, it will not change the way messages from white- or blacklisted email addresses are handled. Messages from whitelisted email addresses will be delivered directly to your mailbox, and messages from blacklisted email addresses will be automatically classified as spam by the SpamAssassin filter. More details about the white and black lists are available in our White and Black listing section article.

Spamdyke is a spam protection program that filters incoming messages at the SMTP level by blocking connections from mail servers identified as spam sources or that match certain reverse DNS validation rules. The Spamdyke program is enabled by default. You can enable or disable Spamdyke and configure its options from the Control Panel > Mail Manager section under the Global mail settings tab. Spamdyke can be configured only globally for the hosting account; it cannot be managed per mailbox. Note: Messages filtered by the Spamdyke program are blocked at the SMTP level, so such blocked messages will not be delivered to your Junk Mail folder and will not be delivered if the sender is whitelisted for your hosting account or mailbox. Spamdyke uses several methods to determine whether a sending server can be identified as a spam source: Reverse DNS check Graylisting/Greylisting (optional) Reverse DNS check Messages originating from a sending mail server without valid reverse DNS record will be blocked and returned to the sender with the following error: 554 Refused. You have no reverse DNS entry.If you are not our customer and receive the above error when sending to a server maintained by us, the SMTP server you use does not have a valid reverse DNS record/name. You need to contact the administrator of your mail server to have the DNS entry fixed, or you need to use another SMTP (outgoing) mail server. If you receive the above message while trying to send a message through the SMTP server of your hosting account, please change the port of the outgoing server from 25 to 587. Graylisting/Greylisting (optional) Spamdyke can also be configured to use Graylisting. Graylisting is the technique of denying mail delivery the first time a sender tries to deliver to a recipient. The next time the remote server attempts to deliver the message, it is accepted. All future messages from the sender to the recipient are also allowed. With Graylisting enabled, our mail server will "temporarily reject" any messages from a sender it does not recognize. The originating server will try a new delivery, usually in a few minutes, and if the message is legitimate, it will be accepted. If the message is from a spammer, it will probably not be retried as spammers go through thousands of email addresses and cannot afford the time delay to retry a particular message. Standard mail servers, however, always attempt to deliver messages again if they are rejected with such a "temporary" error message, in accordance with the SMTP RFC specifications. When a recipient/sender pair is marked as temporarily allowed, its status will remain for a given period. New messages sent within this period will refresh its duration. Once this period expires, the recipient/sender pair will undergo the Graylisting check.The only downside of the Graylisting technique is that some messages may be received with delay which will depend on waiting period before the sending server tries to re-send the message. Graylisting is not enabled by default, so if you wish to use it, you need to enable it through the Control Panel > Mail Manager section under the Global mail settings tab. Information about all messages processed by Spamdyke is recorded in the mail server logs which are accessible via the Mail logs subsection of the Control Panel > Logs section.

The Header filters subsection of the hosting Control Panel's Mail Manager section allows you to selectively filter out incoming email messages based on the contents of their headers. Email message headers are added to a message by the sending email software, and most of them are visible only when you view the email message source. Instructions on how to view the full message headers in some of the most popular email software applications are available in our Viewing e-mail message headers article. Please note that using header filters requires some general knowledge of how the email system works. Step-by-step instructions on how to add header filters are available in our Adding header filters article. You can find information about the available filtering options and a description of the message headers below: Filter action Filter condition(s) Headers Comparison String Filter priority Additional filtering (action for all non-filtered messages) Filter action You can select from the following actions which will be taken when the header filter matches a message: Junk mail — puts the message in the Junk Mail folder of the mailbox. If the Junk Mail folder is not enabled for the mailbox and the filter matches a message, the Drop mail action will be applied for the message. Drop mail — deletes the message silently (without sending a notification to the sender about the failed delivery). Move mail — moves the message to a folder in the mailbox (a drop-down menu will be displayed where you can select the desired folder). Forward mail — forwards the message to another recipient. An input field will be displayed next to the action drop-down menu where you can enter the email address of the recipient/s. You can enter up to five email addresses, separated by a comma. Filter condition(s) The filter conditions allow you to define the exact criteria for matching in the incoming message - header, string, and comparison. You can add conditions by using the +Add button, and you can use up to five conditions for a single filter. To remove a condition, click on the Trash icon next to it. Headers You can select the email header that should be matched by the filter from a predefined list. If you wish to add a custom header, select the last option (named Enter custom header) from the predefined list, and enter the header name in the email header input field. The available email headers for selection from the predefined list are: Subject — contains the subject of the message. If you want to filter all messages that contain a specific word in the subject, select this option. From — contains the sender email address and name (if provided by the sender). To — contains the recipient email address and name (if provided by the sender). This would usually be your email address. CC — contains the email addresses of additional recipients of the message. CC stands for Carbon Copy which is used in most email clients for this purpose. Received — contains the IP address of the sender and is actually added by the mail server. If you want to block all messages from a given IP address, use this option. X-Spam-Level — contains the spam score of the message which is calculated by SpamAssassin (email scanning software). This header will not be added to your incoming messages if you are using our implementation of SpamAssassin. If you are using third-party filtering services (SpamCop.net for example), you can take advantage of this setting. X-Mailer — identifies the email software application used for sending the email message. If you select this option and type Outlook, you will filter all incoming messages that have been sent through MS Outlook and Outlook Express. X-Mailscanner — added by anti-virus software such as Mailscanner. We have added it upon user request because a particular virus was adding this header to all incoming messages, and banning messages with this header would ban all such viruses. However, it might also ban messages that have been scanned by Mailscanner, so we do not recommend using this option. Content-type — shows the structure of the message. It could be plain text, HTML, MIME encoded, etc. Attachment- allows you to filter messages that contain or do not contain any attachments or a specific attachment type. Attachment types are combined in several categories. In the table below, you can check what file types are included in each category: Archive file 7z, 7zip, 7zip2, ace, alz, apk, arc, arj, ark, bz2, bzip, bzip2, cab, gz, gz2, gzip, gzip2, img, iso, lz, lzh, lzma, lzo, lzx, rar, rz2, sea, sfx, sqx, tar, tgz, vhd, vhdx, xz, xz2, zip, zip2, zipx Image file bmp, exif, gif, jfif, jpe, jpeg, pcx, png, svg, tif, tiff Audio file aac, flac, m4a, m4p, mp3, ogg, ra, wav, wma Video file 3gp, asf, asx, avi, divx, flc, flv, flx, h264, m4e, m4v, mkv, mp4, mpeg, mpeg(1-9), mpg, ogm, ogv, ogx, rm, vob, webm, wmv, xvid Document file csv, doc, docx, epub, htm, html, log, ods, odt, ppt, pptx, txt, xhtml, xls, xlsx, xml PDF file pdf Executable file bat, bin, cmd, com, cpl, deb, dll, elf, exe, gadget, hta, inf, jar, js, jse, msc, msh, msi, msp, pif, ps1, reg, rpm, scf, scr, sh, so, sys, vb, vbe, vbs, ws, wsc, wsf, wsh   Enter custom header — allows you to enter headers that are not available for selection from the predefined list. Comparison Next to the header selection, you will find the header comparison drop-down menu which allows you to specify how the filter should match the specified header. The available options are: contains doesn't contain is isn't begins with doesn't begin with ends with doesn't end with String You can enter the exact match string in the input field next to the comparison menu. The match string does not require an exact word match, so if you are using hi as a match string, the words high and Ohio will be considered a successful match. Wildcards are not supported when adding a header filter. Filter priority Right below the Header filters subsection of the hosting Control Panel's Mail Manager section, you will find the Active filters subsection where all your currently active filters will be listed. If you have more than one active filter, the filters will be processed from top to bottom. The filter at the top will have the highest priority, so it will be checked first for matching, and the filter at the bottom will have the lowest priority, so it will be checked last, after all the other filters. By default, new filters will be added with the highest priority (at the top of the active filters list). If you wish to change the priority of the header filters, click on the  Filter priority goes from top (highest) to bottom (lowest). Click here to unlock and rearrange filters. link. This will unlock the active filter list, and you will be able to change the position of the filters by using the drag-and-drop method or up/down arrow keys next to each filter. The active filters list will always be in a locked state when you open the page. Only the first filter that matches a message will be processed. Any matching filters with lower priority will be ignored. If Additional filtering (see below) is enabled, the filter for non-filtered messages always have the lowest priority, and this cannot be changed. Additional filtering (action for all non-filtered messages) Through the Additional filtering subsection of the hosting Control Panel's Mail Manager section, you can create a filter for your mailboxes that will perform a Filter action for all messages that do not match any of your active header filters. Please use this feature with caution as if you add a default local filter for the mailbox, none of the global filters will be processed for that mailbox.

Our mail system utilizes a database, which contains IP addresses and networks that are known sources of unsolicited mail messages. Mail from these servers is rejected from our machines. The database that we use is extremely precise and is updated real-time.

This FAQ item explains how the White and Black listing section works. The White and Black listing section allows blacklisting or whitelisting email addresses based on the Envelope Sender/Recipient. Generally, the Envelope Sender/Recipient are the addresses that are used in the communication between email servers. The Envelope Sender would show the sender that is set by the sending email server. On our servers, the Envelope Sender is set as Return-Path of the message, and when viewing the source of an email message received on our servers, the Return-Path header would be the Envelope Sender from the SMTP communication between email servers. The Envelope Recipient would be the mailbox that will receive the message. Note that you may even not see this Envelope Recipient in the message itself. For example, if the sender uses a blind carbon-copy (BCC), it is possible that you would see a TO header in the message source, while the message could be received in a completely different mailbox (due to the BCC used when sending). On the other side, the From and To addresses in the message headers are set by the sender, and they could be easily forged. That's why most spam messages have incorrect From and To headers. Generally, message headers are not a reliable way of blocking spammers, because manipulating message headers is a very common spam-sending technique. The White and Black listing section works on two levels: Global level for all mailboxes on the account, through the Edit Global Mail Settings of the hosting Control Panel's Mail Manager section. Local level for each mailbox, through the Filters section next to the mailbox. If you want to block messages based on From/To headers, you can do this through the Header Filters section.

This article is intended to warn you of the dangers of whitelisting or blacklisting your domain name or your mailbox using the SpamAssassin white and black listing functionality. If you whitelist your domain name or mailbox as a sender, it will increase the number of spam messages reaching your mailbox. The spammers use the so-called "header spoofing" technique that allows them to use any e-mail address as From and Return-Path, whether or not they have access to the mail server for that domain. This is a flaw of the global SMTP protocol. If you whitelist your domain name or mailbox as a recipient, it will stop the SpamAssassin and header filters spam protection. All messages sent to the mailbox will bypass the SpamAssassin and the header filters. If you blacklist your domain name or mailbox as a sender, it will prevent you from sending messages from your domain or mailbox to yourself. If you blacklist your domain name or mailbox as a recipient, it will stop the delivery of all email messages to the domain or the mailbox.