Stefan Pollard at ClickZ has put together some tips on best practice in allowing recipients to unsubscribe from emails. This is important, as subscribers will most likely mark your emails as spam if they have any trouble unsubscribing.
Email marketers should therefore make the process of unsubscribing from emails as easy and trustworthy as possible, as if ISPs get too many complaints around your emails, this could seriously damage your sender reputation.
Stefan’s tips are:
Use an unsubscribe procedure that requires as few steps as possible
Unsubscribing should be a one or two step process at most, and you should not require customers to add any further login details.
Making customers jump through too many hoops to unsubscribe, as in this email worst practice example, can damage your brand in their eyes, and will often lead them to report your emails as spam instead.
Tell users exactly how they got onto your list
Remind customers exactly how and where they signed up to receive your emails. Otherwise, they may perceive you as a spammer.
Place the unsubscribe message where people can see it
Making customers look too hard for the unsubscribe link will have them reporting you as spam. Stefan recommends placing it in the admin section, where people will expect to find it, or else display it prominently elsewhere in the message.
Test your unsubscribe procedure
Make sure the process works by clicking the links or sending test emails.
Provide alternate unsubscription methods
If people have difficulty unsubscribing online, or don’t want to, give them a phone number to call, or a postal address to send the request to.
Email users savvy about managing inboxes - survey
Email Marketing - Roundtable Briefing, May 2007