Strange mails with action mailer

Hey people,

I am sending email through my rails applications, using templates that
exists in the database. I have both a html and a text version of the
mail which I send both. The thing is, that for some of my users the mail
looks really strange. And example of the beginning of such a mail is
this:

—mimepart_46e50be2897e2_2b94…fdab406ea968

Content-Type: text/plain; charset=utf-8

Content-Transfer-Encoding: Base64

Content-Disposition: inline

TS4gTGF6YXJldmljIFZlcndlaWogaGVlZnQgZWVuIGJyb2NodXJlIGFhbmdl

dnJhYWdkLg0KDQpDb250YWN0IGdlZ2V2ZW5zOg0KDQpCZWRyaWpmOiBSZXN0

YXVyYW50IEFkcmlhdGljbw0KRW1haWw6IG1sYXphcmV2aWNAaG9tZS5ubA0K

VGVsZWZvb246IDA3Ny0zODIyOTk1DQpGYXg6IDA3Ny0zOTY3NzU4DQoNCk9w

bWVya2luZ2VuOg0KSWsgem91IGdyYWFnIG1lZXIgd2V0ZW4gb3ZlciBkZSB3

ZXJrd2lqemUgdmFuIHN0dWRlbnRlbndlcmsgZW4gZGUgdGFyaWV2ZW4=

—mimepart_46e50be2897e2_2b94…fdab406ea968

Content-Type: text/html; charset=utf-8

Content-Transfer-Encoding: Quoted-printable

Content-Disposition: inline

Any suggestions/ideas??

Thanks!