Effective email marketing campaigns require proper timing, deep knowledge of your audience, and plenty of restraint.

Email marketers must walk a fine line when crafting newsletters and other messages. Your missives can be a welcome promotion, filled with information of real interest to subscribers and sent infrequently enough to remain unobtrusive–or they can be just another inbox-clogging nuisance. Here are the most important tips from Mashable on getting subscribers engaged and keeping them from clicking the dreaded “unsubscribe” link.

Pay attention to timing
Not only does the message itself need to be timely to resonate with subscribers, but it’s important to send it at the right time. Mashable cites a recent survey by Experian Marketing Services that finds emails sent on Saturdays and Sundays receive the most clicks and yield the highest revenue-per-email rate. Late nights are also good–with a lower volume of competing messages, emails sent between 8 p.m and 4 a.m. garner the highest response rate. You’ll need to do some testing to determine the optimal times.

Personalize the message
Sending out a single email blast to all subscribers may save time, but it’s a poor way to make a real connection with them. It’s far more effective to break the list into groups based on demographics or behavior from the user data you’ve collected. The more relevant you can make the message to each individual recipient, the more likely they’ll be to engage with it.

Don’t forget mobile users
A huge portion of your audience will receive your email newsletter on a mobile device, so making the text readable and the links clickable is crucial. That may seem obvious in this mobile-dominated era, but a study by software company Equinux earlier this year found that less than 12 percent of major brands’ newsletters were optimized for viewing on mobile displays.

Acknowledge when a subscriber engages
To maintain the connection with subscribers, send an appreciative response when they sign up, as well as the first time they make a purchase or engage with your email materials in some other way. Just be careful not to bombard them with follow-up messages–sending too much email is the surest way to lose new subscribers.

Give an “opt-down” option
Another way to avoid email overkill is letting customers choose to receive fewer newsletters or other messages. When someone on your list indicates that s/he wants to unsubscribe, present this as an alternative.

Expect to lose some people
No matter how useful and well tailored your campaign is, you’re going to lose some subscribers, most often within 30 days of their sign-up date. It’s an inevitable part of email marketing, but one that you can minimize. When people opt to unsubscribe, ask them to fill out an exit survey where they can click a button to indicate their reasons for leaving and fill in a field to give more specific feedback. Collecting this information can prove vital for preventing the loss of other customers in the future.