We used to use another cold email outreach tool, Quickmail, which has a very useful and simple feature for client marketing outreach. It's called "cancel colleagues upon reply".
Basically, if I'm emailing multiple hiring contacts at a potential client firm and one person from that domain replies, it will cancel outreach on that campaign to the other contacts upon reply. This way my campaign doesn't continue nagging the rest of the team if one decision-maker replies.
I miss this feature for marketing outreach, and would love to see something similar implemented in Sourcewhale. This feature is literally the only reason I haven't completely let go of QuickMail.
Obviously this only applies to marketing campaigns and not to candidate / recruiting campaigns. For example if you're emailing candidates from a given firm at their work address, you want those to continue sending regardless of whether one candidate replies or not.
Thanks for your consideration,
Matt Fox