Email and email validation technologies continue to evolve and it is increasingly important that businesses keep up with these changes to ensure they are protected and getting the most out of their email lists. Whether the intention is to verify emails for a mailing campaign, verify users when they sign up on a webpage or ensure that your data is compliant with privacy laws like the General Data Protection Regulation (GDPR), our DOTS Email Validation 3 service helps ensure your email data is accurate, valid, and up-to-date.

In our Applications Engineer department, we are proud of our product expertise and happy to work with you and make integration recommendations that best meet your needs. We have found that each use case and integration scenario is different and may require using different parts of the email validation service to achieve best results. We always recommend starting with a free API key and checking out our comprehensive and up-to-date developer guide for a strong understanding of everything our service can do. With that said, below are some of the most common discussions we have with our clients when integrating our Email Validation service.

Setting up Email Validation’s Web Service Call

Our recommended operation for the service is the ValidateEmailAddress operation. This method has four input fields; EmailAddress, AllowCorrections, Timeout and LicenseKey. The EmailAddress field should be the email address to be validated and the License key should be the trial or production key supplied by Service Objects (you can get yours here). The AllowCorrections and Timeout fields can be used to fine-tune the results from our email validation service.

The AllowCorrections field will essentially tell the service whether to attempt a correction on the email address if the original one is found to be invalid. This is helpful, especially for scenarios where the user mistypes their email address. This can also be set to “false” to weed out users that do not “strongly” type their email addresses.

The Timeout value uses a number in milliseconds. This value sets the maximum amount of time for our services to communicate with a mail server in a given request. One of the key features of our service is that it performs real-time SMTP communication with mail servers and part of this communication is waiting for the mail server to respond. So in short, the longer the timeout, the greater the validation accuracy will be. This will help turn the unknown email addresses (score 2; more on this below) into either good or bad emails. Most mail servers will respond very quickly to communication, but smaller or lesser known servers can take a bit of time to respond.

Email Validation Scoring

There are a lot of different results returned in the Email Validation service and the best use case depends on your business logic and what you are hoping to achieve with the service. Arguably, the first return you will want to look at would be the score value that is returned, below are the scores and a brief description.

Score	Description
0	Email is Good
1	Email is Probably Good
2	Unknown
3	Email is Probably Bad
4	Email is Bad

Generally, we recommend that our clients accept emails with a score of 0, 1 or 2 as “good” emails. If you want to be more conservative with email campaigns then only including emails with scores of 0 or 1 would be the way to go. This may not be the best option if you are validating users that fill in a form on your webpage, as many popular catch-all domains (e.g. yahoo, hotmail, etc.), will return an Unknown (2) score from the service. Conversely, considering good emails as scores from 0 to 3 would be an option if you want the highest volume of possible good emails.

Warning Codes

The Email Validation service also returns Warning and Note codes for each email that is validated. Generally speaking, the Warning codes help define what is detrimental to the email score. Warning flags like Bot, Vulgar, Garbage and DisposableEmail are obvious indicators of a bad email address. But a warning flag like “KnownGreylister” indicates that the mail server is known to use greylisting techniques but this doesn’t necessarily mean the email address is bad. If you are sending an email campaign through MailChimp, Marketo or similar platforms, then you may experience temporary bounce backs on email addresses with the KnowGreylister flag, as those email domains will give a temporary reject message due to unfamiliar mail servers.

There are over 20 Warning codes that our Email Validation service can return, see the table below for the complete list and a brief description of each.

Code	Warning Name	Description
0	UnrecognizedTLD	Indicates if the top-level-domain is not recognized by ICANN.
1	InvalidSyntax	Indicates if the email is syntactically invalid.
2	InvalidDomainSpecificSyntax	Indicates if email is syntactically invalid for the given domain.
3	InvalidDNS	Indicates if the domain is unregistered or it does not have at least one MX or A record configured to relay email.
4	NoMXRecords	Indicates that the registered DNS does not have an MX record.
5	Established	Indicates that the email address is known to be in bulk marketing lists.
6	Alias	Indicates if the email address is believed to be an alias address.
7	Bogus	Indicates if the email address is believed to be a bogus email. For example, asdf@asdf.com.
8	BogusSMSAddress	Indicates if the email address is believed to be a bogus SMS domain address.
9	Garbage	Indicates if the email address is believed to contain garbage-like keyboard strokes and/or garbage-like characters.
10	Vulgar	Indicates if vulgar words or content are found in the email address.
11	MailBoxIsFull	Indicates if the mailbox is currently full and unable to receive any new messages.
12	MailboxIsBusy	Indicates if the mailbox is reported by the hosting mail server as being busy and unable to currently accept new messages.
13	DisposableEmail	Indicates if the email address is believed to be disposable. Disposable email address are generally only valid for a short period of time before they are disposed and are then no longer valid.
14	SpamTrap	Indicates if the mailbox is believed to be a spam trap.
15	KnownSpammer	Indicates if the email address is known to have participated in spam-like activities.
16	BlacklistedDomain	Indicates if the domain was found to be in one or more blacklists.
17	KnownComplainer	Indicates if the email address has been identified as a known complainer of receiving unsolicited mail.
18	KnownGreylister	Indicates if the mail server is known to commonly use greylisting techniques. This means that if your mail server is communicating with this domain for the first time or if you are sending bulk messages or messages in high frequency then you may be greylisted by them and experience temporary bounce backs.
19	OptInRequired	Indicates if the mail server requires opting-in to send and receive messages.
20	IsWhiteListOnly	Indicates if the mail server only relays messages for users that are whitelisted.
21	ConnectionRefused	Indicates if the mail server refuses to accept an SMTP connection.
22	Email is Bad - Subsequent checks halted.	Indicates that the email address failed a critical check, such as SMTP verification.
23	Bot	Indicates that the email address has been reported as being a known bot.

Note Codes

Notes from Email Validation typically provide additional information about an email domain and can be leveraged to intelligently target specific email addresses. For example, if you have an email sign up form and you want to limit the sign-ups to business emails, then you might want to want to look for email addresses with the BuisnessAddress note flag, which would indicate that the email is likely associated with a business. Or maybe you want to identify country based email addresses? Then it may be wise to filter out emails that receive the CCTLD note code as these will indicate emails that have a Top-Level Domain (i.e. .com of example@serviceobjects.com) that is associated with a specific country.  In addition, we recently rolled out a new feature that can detect the geographic location of the email’s mail server.

Other Note Codes you may want to pay attention to are those indicating the service had trouble connecting to the mail server.  While these notes don’t indicate that an email is bad, they do reflect simulated interactions with mail servers and may indicate trouble contacting customers via email campaign or through typical email delivery. You can see the complete list of Note Codes and their descriptions below.

Code	Note	Description
0	CCTLD	Indicates if the top-level-domain (tld) represents a specific country. For example ".us" implies United States.
1	Free	Indicates if the domain of the email is a public-register domain, where users can sign up for email accounts for free.
2	SMSDomain	Indicates if the domain is a known Mail-to-SMS Gateway.
3	Role	Indicates if the email address appears to be a role that is designed to be anonymously managed by one or more persons.
4	BusinessAddress	Indicates if the email address appears to be work related.
5	GreyListed	Indicates if the mail server responded with a known greylist tactic.
6	MailServerTemporarilyUnavailable	Indicates that the mail server may be temporarily unavailable or too busy to respond.
7	ServerConnectTimeout	Indicates that a connection to the recipient mail server could not be established.
8	MailBoxTimeout	Indicates that the connection to the mail server timed out when trying to verify the email address.
9	TemporaryReject	Indicates that the email address was temporarily rejected by the mail server. This is also known as a soft-bounce and the rejection is not permanent. There are many reasons for why a mail server may respond with a temporary reject. The mailbox or server may be busy, unavailable, or using a greylist. When a mail server does this it typically wants you to wait at least 15 minutes and then try again later.
10	SlowMailServer	Indicates that the host mail server is known to communicate slowly and that real-time verification of an email address may not be possible unless adequate time is provided. In some cases a timeout time of 90 seconds or more may be necessary to verify email addresses with these mail servers.
11	Varies (Example: JP)	Countries: The ISO2 country code for the country where the mail server(s) is located. If mail servers are found in more than one country, then all country ISO2 codes will be represented in a pipe-delimited list. ***In BETA
12	Varies (Example: OS|TY)	Region: The region in the country where the mail server(s) is located. The region is commonly returned as a two-character abbreviation. If mail servers are found in more than one region then the value will be a pipe-delimited list of the regions. ***In BETA
13	Varies (Example: Osaka|Tokyo)	Localities: The name of the locality where the mail sever(s) is located in. If mail servers are found in more than one locality then the value will be a pipe-delimited list of all the localities. ***In BETA
14	Varies (Example: 543-0062 | 102-0082)	PostCodes: The post code of where the mail server(s) is located. If multiple post codes are found, then the value will be a pipe-delimited list. ***In BETA

Our Email Validation service is robust, multi-featured and constantly under refinement. Don’t hesitate to schedule an integration call with our Applications Engineering team with any integration or best practices questions, we are glad to help.