Having a pen pal is an amazing way to connect with someone from a different culture and country. However, using the term "hadst pen pal" may sound a bit outdated and formal. Instead, you could use any of the following synonyms to express the same idea: "corresponded with a pen pal", "exchanged letters with a pen pal", "kept in touch with a pen pal", "maintained a pen pal relationship", "communicated with a pen pal", or "wrote to a pen pal". All of these choices are more modern and colloquial and convey the same message. So why not pick one and start talking about your pen pal experience today!