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Salesforce

Intercom

Hubspot

Nethunt

Cirrus Insight

Buzzstream

Close.io

FreshMail

ActiveCampaign

Marketo

Zendesk Sell

ContactMonkey

MixMax

Outreach

个人邮件追踪服务商：

Superhuman

Gem

Getnotify

Mailspring

Yesware

Polymail

Mailtrack

Streak

Boomerang

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GrowthDot

批量邮件发送服务商：

Mailgun

Mandrill

Mailjet

YAMM

Getresponse

Contact Monkey

AWeber

Return Path

Sendgrid

Postmark

邮件营销服务商：

Campaign Monitor

MailChimp

ConvertKit

TinyLetter

Constant Contact

Sendy

Litmus

Klaviyo

Emarsys

Critical Impact

iContact

Mixpanel

phpList

Sailthru

Thunderhead