Katy Perry has sent ex-husband Russell Brand a congratulatory message to celebrate his 10 years off drugs.

The 'Wide Awake' hitmaker - who divorced the British comedian in December 2011 after 14 months of marriage - sent the 37-year-old actor an email detailing how ''proud'' she is of him for being sober for a decade and told him her heart is ''finally healing'' following their split.

A source told The Sun newspaper: ''Although they've broken up, Katy knows how important this milestone is for Russell.

''She wanted to let him know that she was thinking of him and that she was still proud of what he has achieved.

''She also wanted to drop him the email to wish him a happy 2013 and to let him know that her heart was finally healing.''

Russell, who previously battled a heroin addiction, recently took to his Twitter account to reveal he had been clean for 10 years and encouraged others to try to do the same.

The comic - who also thanked 'Rock of Ages' promoter Nicola Schuller for helping him with the musical movie, in which he plays Sunset Strip nightclub manager Lonnny Barnett - wrote: ''10 years clean today. Thanks for all your messages of love. Thanks@schullerinc for the film. Anyone can get clean, one day at a time. (sic)''

In August, Russell - whose divorce from Katy was finalised in July - starred in a TV documentary 'Russell Brand: From Addiction to Recovery' in which he watched old footage of himself doing drugs and explained how his addiction blighted his life.